Vulnerabilities > CVE-2019-11503 - Link Following vulnerability in Canonical Snapd
Attack vector
NETWORK Attack complexity
LOW Privileges required
NONE Confidentiality impact
NONE Integrity impact
HIGH Availability impact
NONE Summary
snap-confine as included in snapd before 2.39 did not guard against symlink races when performing the chdir() to the current working directory of the calling user, aka a "cwd restore permission bypass."
Vulnerable Configurations
Common Weakness Enumeration (CWE)
Common Attack Pattern Enumeration and Classification (CAPEC)
- Symlink Attack An attacker positions a symbolic link in such a manner that the targeted user or application accesses the link's endpoint, assuming that it is accessing a file with the link's name. The endpoint file may be either output or input. If the file is output, the result is that the endpoint is modified, instead of a file at the intended location. Modifications to the endpoint file may include appending, overwriting, corrupting, changing permissions, or other modifications. In some variants of this attack the attacker may be able to control the change to a file while in other cases they cannot. The former is especially damaging since the attacker may be able to grant themselves increased privileges or insert false information, but the latter can also be damaging as it can expose sensitive information or corrupt or destroy vital system or application files. Alternatively, the endpoint file may serve as input to the targeted application. This can be used to feed malformed input into the target or to cause the target to process different information, possibly allowing the attacker to control the actions of the target or to cause the target to expose information to the attacker. Moreover, the actions taken on the endpoint file are undertaken with the permissions of the targeted user or application, which may exceed the permissions that the attacker would normally have.
- Accessing, Modifying or Executing Executable Files An attack of this type exploits a system's configuration that allows an attacker to either directly access an executable file, for example through shell access; or in a possible worst case allows an attacker to upload a file and then execute it. Web servers, ftp servers, and message oriented middleware systems which have many integration points are particularly vulnerable, because both the programmers and the administrators must be in synch regarding the interfaces and the correct privileges for each interface.
- Leverage Executable Code in Non-Executable Files An attack of this type exploits a system's trust in configuration and resource files, when the executable loads the resource (such as an image file or configuration file) the attacker has modified the file to either execute malicious code directly or manipulate the target process (e.g. application server) to execute based on the malicious configuration parameters. Since systems are increasingly interrelated mashing up resources from local and remote sources the possibility of this attack occurring is high. The attack can be directed at a client system, such as causing buffer overrun through loading seemingly benign image files, as in Microsoft Security Bulletin MS04-028 where specially crafted JPEG files could cause a buffer overrun once loaded into the browser. Another example targets clients reading pdf files. In this case the attacker simply appends javascript to the end of a legitimate url for a pdf (http://www.gnucitizen.org/blog/danger-danger-danger/) http://path/to/pdf/file.pdf#whatever_name_you_want=javascript:your_code_here The client assumes that they are reading a pdf, but the attacker has modified the resource and loaded executable javascript into the client's browser process. The attack can also target server processes. The attacker edits the resource or configuration file, for example a web.xml file used to configure security permissions for a J2EE app server, adding role name "public" grants all users with the public role the ability to use the administration functionality. The server trusts its configuration file to be correct, but when they are manipulated, the attacker gains full control.
- Manipulating Input to File System Calls An attacker manipulates inputs to the target software which the target software passes to file system calls in the OS. The goal is to gain access to, and perhaps modify, areas of the file system that the target software did not intend to be accessible.
Nessus
NASL family Fedora Local Security Checks NASL id FEDORA_2019-B6612C5FE5.NASL description #### Update to v1.48 - New API : - `snapd_client_get_connections_async` - `snapd_client_get_connections_finish` - `snapd_client_get_connections_sync` - `snapd_client_get_interfaces2_async` - `snapd_client_get_interfaces2_finish` - `snapd_client_get_interfaces2_sync` - `snapd_client_get_snap_conf_async` - `snapd_client_get_snap_conf_finish` - `snapd_client_get_snap_conf_sync` - `snapd_client_set_snap_conf_async` - `snapd_client_set_snap_conf_finish` - `snapd_client_set_snap_conf_sync` - `snapd_connection_get_gadget` - `snapd_connection_get_interface` - `snapd_connection_get_manual` - `snapd_connection_get_plug` - `snapd_connection_get_plug_attribute` - `snapd_connection_get_plug_attribute_names` - `snapd_connection_get_slot` - `snapd_connection_get_slot_attribute` - `snapd_connection_get_slot_attribute_names` - `snapd_connection_has_plug_attribute` - `snapd_connection_has_slot_attribute` - `snapd_interface_get_doc_url` - `snapd_interface_get_name` - `snapd_interface_get_plugs` - `snapd_interface_get_slots` - `snapd_interface_get_summary` - `snapd_markdown_node_get_children` - `snapd_markdown_node_get_node_type` - `snapd_markdown_node_get_text` - `snapd_markdown_parser_new` - `snapd_markdown_parser_get_combine_whitespace` - `snapd_markdown_parser_parse` - `snapd_markdown_parser_set_combine_whitespace` - `snapd_plug_get_connected_slots` - `snapd_plug_ref_get_plug` - `snapd_plug_ref_get_snap` - `snapd_slot_get_connected_plugs` - `snapd_slot_ref_get_slot` - `snapd_slot_ref_get_snap` - `SNAPD_ERROR_OPTION_NOT_FOUND` - Deprecated API : - `snapd_client_get_interfaces_async` - `snapd_client_get_interfaces_finish` - `snapd_client_get_interfaces_sync` - `snapd_connection_get_name` - `snapd_connection_get_snap` - `snapd_plug_get_connections` - `snapd_slot_get_connections` - Allow searching via common-id - Add a description markdown parser - Replace `SnapdConnection` with `SnapdPlugRef` and `SnapdSlotRef` - Support updated connections API (`/v2/connections`) - Support updated `/v2/interfaces&select=` API - Support snap configuration API - Add Qt interface attribute API - Make `snapd_client_set_socket_path` revert to the default when `NULL` passed. - Fix C99 mode not being enabled on older versions of GCC Note that Tenable Network Security has extracted the preceding description block directly from the Fedora update system website. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues. last seen 2020-06-01 modified 2020-06-02 plugin id 126662 published 2019-07-15 reporter This script is Copyright (C) 2019-2020 and is owned by Tenable, Inc. or an Affiliate thereof. source https://www.tenable.com/plugins/nessus/126662 title Fedora 30 : snapd-glib (2019-b6612c5fe5) code # # (C) Tenable Network Security, Inc. # # The descriptive text and package checks in this plugin were # extracted from Fedora Security Advisory FEDORA-2019-b6612c5fe5. # include("compat.inc"); if (description) { script_id(126662); script_version("1.3"); script_cvs_date("Date: 2020/01/08"); script_cve_id("CVE-2019-11503"); script_xref(name:"FEDORA", value:"2019-b6612c5fe5"); script_name(english:"Fedora 30 : snapd-glib (2019-b6612c5fe5)"); script_summary(english:"Checks rpm output for the updated package."); script_set_attribute( attribute:"synopsis", value:"The remote Fedora host is missing a security update." ); script_set_attribute( attribute:"description", value: "#### Update to v1.48 - New API : - `snapd_client_get_connections_async` - `snapd_client_get_connections_finish` - `snapd_client_get_connections_sync` - `snapd_client_get_interfaces2_async` - `snapd_client_get_interfaces2_finish` - `snapd_client_get_interfaces2_sync` - `snapd_client_get_snap_conf_async` - `snapd_client_get_snap_conf_finish` - `snapd_client_get_snap_conf_sync` - `snapd_client_set_snap_conf_async` - `snapd_client_set_snap_conf_finish` - `snapd_client_set_snap_conf_sync` - `snapd_connection_get_gadget` - `snapd_connection_get_interface` - `snapd_connection_get_manual` - `snapd_connection_get_plug` - `snapd_connection_get_plug_attribute` - `snapd_connection_get_plug_attribute_names` - `snapd_connection_get_slot` - `snapd_connection_get_slot_attribute` - `snapd_connection_get_slot_attribute_names` - `snapd_connection_has_plug_attribute` - `snapd_connection_has_slot_attribute` - `snapd_interface_get_doc_url` - `snapd_interface_get_name` - `snapd_interface_get_plugs` - `snapd_interface_get_slots` - `snapd_interface_get_summary` - `snapd_markdown_node_get_children` - `snapd_markdown_node_get_node_type` - `snapd_markdown_node_get_text` - `snapd_markdown_parser_new` - `snapd_markdown_parser_get_combine_whitespace` - `snapd_markdown_parser_parse` - `snapd_markdown_parser_set_combine_whitespace` - `snapd_plug_get_connected_slots` - `snapd_plug_ref_get_plug` - `snapd_plug_ref_get_snap` - `snapd_slot_get_connected_plugs` - `snapd_slot_ref_get_slot` - `snapd_slot_ref_get_snap` - `SNAPD_ERROR_OPTION_NOT_FOUND` - Deprecated API : - `snapd_client_get_interfaces_async` - `snapd_client_get_interfaces_finish` - `snapd_client_get_interfaces_sync` - `snapd_connection_get_name` - `snapd_connection_get_snap` - `snapd_plug_get_connections` - `snapd_slot_get_connections` - Allow searching via common-id - Add a description markdown parser - Replace `SnapdConnection` with `SnapdPlugRef` and `SnapdSlotRef` - Support updated connections API (`/v2/connections`) - Support updated `/v2/interfaces&select=` API - Support snap configuration API - Add Qt interface attribute API - Make `snapd_client_set_socket_path` revert to the default when `NULL` passed. - Fix C99 mode not being enabled on older versions of GCC Note that Tenable Network Security has extracted the preceding description block directly from the Fedora update system website. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues." ); script_set_attribute( attribute:"see_also", value:"https://bodhi.fedoraproject.org/updates/FEDORA-2019-b6612c5fe5" ); script_set_attribute( attribute:"solution", value:"Update the affected snapd-glib package." ); script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:N/I:P/A:N"); script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C"); script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"); script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C"); script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available"); script_set_attribute(attribute:"plugin_type", value:"local"); script_set_attribute(attribute:"cpe", value:"p-cpe:/a:fedoraproject:fedora:snapd-glib"); script_set_attribute(attribute:"cpe", value:"cpe:/o:fedoraproject:fedora:30"); script_set_attribute(attribute:"vuln_publication_date", value:"2019/04/24"); script_set_attribute(attribute:"patch_publication_date", value:"2019/07/13"); script_set_attribute(attribute:"plugin_publication_date", value:"2019/07/15"); script_set_attribute(attribute:"generated_plugin", value:"current"); script_end_attributes(); script_category(ACT_GATHER_INFO); script_copyright(english:"This script is Copyright (C) 2019-2020 and is owned by Tenable, Inc. or an Affiliate thereof."); script_family(english:"Fedora Local Security Checks"); script_dependencies("ssh_get_info.nasl"); script_require_keys("Host/local_checks_enabled", "Host/RedHat/release", "Host/RedHat/rpm-list"); exit(0); } include("audit.inc"); include("global_settings.inc"); include("rpm.inc"); if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED); release = get_kb_item("Host/RedHat/release"); if (isnull(release) || "Fedora" >!< release) audit(AUDIT_OS_NOT, "Fedora"); os_ver = pregmatch(pattern: "Fedora.*release ([0-9]+)", string:release); if (isnull(os_ver)) audit(AUDIT_UNKNOWN_APP_VER, "Fedora"); os_ver = os_ver[1]; if (! preg(pattern:"^30([^0-9]|$)", string:os_ver)) audit(AUDIT_OS_NOT, "Fedora 30", "Fedora " + os_ver); if (!get_kb_item("Host/RedHat/rpm-list")) audit(AUDIT_PACKAGE_LIST_MISSING); cpu = get_kb_item("Host/cpu"); if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH); if ("x86_64" >!< cpu && cpu !~ "^i[3-6]86$") audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, "Fedora", cpu); flag = 0; if (rpm_check(release:"FC30", reference:"snapd-glib-1.48-1.fc30")) flag++; if (flag) { security_report_v4( port : 0, severity : SECURITY_WARNING, extra : rpm_report_get() ); exit(0); } else { tested = pkg_tests_get(); if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested); else audit(AUDIT_PACKAGE_NOT_INSTALLED, "snapd-glib"); }NASL family Fedora Local Security Checks NASL id FEDORA_2019-BC3DFB389F.NASL description #### Update to v1.48 - New API : - `snapd_client_get_connections_async` - `snapd_client_get_connections_finish` - `snapd_client_get_connections_sync` - `snapd_client_get_interfaces2_async` - `snapd_client_get_interfaces2_finish` - `snapd_client_get_interfaces2_sync` - `snapd_client_get_snap_conf_async` - `snapd_client_get_snap_conf_finish` - `snapd_client_get_snap_conf_sync` - `snapd_client_set_snap_conf_async` - `snapd_client_set_snap_conf_finish` - `snapd_client_set_snap_conf_sync` - `snapd_connection_get_gadget` - `snapd_connection_get_interface` - `snapd_connection_get_manual` - `snapd_connection_get_plug` - `snapd_connection_get_plug_attribute` - `snapd_connection_get_plug_attribute_names` - `snapd_connection_get_slot` - `snapd_connection_get_slot_attribute` - `snapd_connection_get_slot_attribute_names` - `snapd_connection_has_plug_attribute` - `snapd_connection_has_slot_attribute` - `snapd_interface_get_doc_url` - `snapd_interface_get_name` - `snapd_interface_get_plugs` - `snapd_interface_get_slots` - `snapd_interface_get_summary` - `snapd_markdown_node_get_children` - `snapd_markdown_node_get_node_type` - `snapd_markdown_node_get_text` - `snapd_markdown_parser_new` - `snapd_markdown_parser_get_combine_whitespace` - `snapd_markdown_parser_parse` - `snapd_markdown_parser_set_combine_whitespace` - `snapd_plug_get_connected_slots` - `snapd_plug_ref_get_plug` - `snapd_plug_ref_get_snap` - `snapd_slot_get_connected_plugs` - `snapd_slot_ref_get_slot` - `snapd_slot_ref_get_snap` - `SNAPD_ERROR_OPTION_NOT_FOUND` - Deprecated API : - `snapd_client_get_interfaces_async` - `snapd_client_get_interfaces_finish` - `snapd_client_get_interfaces_sync` - `snapd_connection_get_name` - `snapd_connection_get_snap` - `snapd_plug_get_connections` - `snapd_slot_get_connections` - Allow searching via common-id - Add a description markdown parser - Replace `SnapdConnection` with `SnapdPlugRef` and `SnapdSlotRef` - Support updated connections API (`/v2/connections`) - Support updated `/v2/interfaces&select=` API - Support snap configuration API - Add Qt interface attribute API - Make `snapd_client_set_socket_path` revert to the default when `NULL` passed. - Fix C99 mode not being enabled on older versions of GCC Note that Tenable Network Security has extracted the preceding description block directly from the Fedora update system website. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues. last seen 2020-06-01 modified 2020-06-02 plugin id 126663 published 2019-07-15 reporter This script is Copyright (C) 2019-2020 and is owned by Tenable, Inc. or an Affiliate thereof. source https://www.tenable.com/plugins/nessus/126663 title Fedora 29 : snapd-glib (2019-bc3dfb389f) code # # (C) Tenable Network Security, Inc. # # The descriptive text and package checks in this plugin were # extracted from Fedora Security Advisory FEDORA-2019-bc3dfb389f. # include("compat.inc"); if (description) { script_id(126663); script_version("1.3"); script_cvs_date("Date: 2020/01/08"); script_cve_id("CVE-2019-11503"); script_xref(name:"FEDORA", value:"2019-bc3dfb389f"); script_name(english:"Fedora 29 : snapd-glib (2019-bc3dfb389f)"); script_summary(english:"Checks rpm output for the updated package."); script_set_attribute( attribute:"synopsis", value:"The remote Fedora host is missing a security update." ); script_set_attribute( attribute:"description", value: "#### Update to v1.48 - New API : - `snapd_client_get_connections_async` - `snapd_client_get_connections_finish` - `snapd_client_get_connections_sync` - `snapd_client_get_interfaces2_async` - `snapd_client_get_interfaces2_finish` - `snapd_client_get_interfaces2_sync` - `snapd_client_get_snap_conf_async` - `snapd_client_get_snap_conf_finish` - `snapd_client_get_snap_conf_sync` - `snapd_client_set_snap_conf_async` - `snapd_client_set_snap_conf_finish` - `snapd_client_set_snap_conf_sync` - `snapd_connection_get_gadget` - `snapd_connection_get_interface` - `snapd_connection_get_manual` - `snapd_connection_get_plug` - `snapd_connection_get_plug_attribute` - `snapd_connection_get_plug_attribute_names` - `snapd_connection_get_slot` - `snapd_connection_get_slot_attribute` - `snapd_connection_get_slot_attribute_names` - `snapd_connection_has_plug_attribute` - `snapd_connection_has_slot_attribute` - `snapd_interface_get_doc_url` - `snapd_interface_get_name` - `snapd_interface_get_plugs` - `snapd_interface_get_slots` - `snapd_interface_get_summary` - `snapd_markdown_node_get_children` - `snapd_markdown_node_get_node_type` - `snapd_markdown_node_get_text` - `snapd_markdown_parser_new` - `snapd_markdown_parser_get_combine_whitespace` - `snapd_markdown_parser_parse` - `snapd_markdown_parser_set_combine_whitespace` - `snapd_plug_get_connected_slots` - `snapd_plug_ref_get_plug` - `snapd_plug_ref_get_snap` - `snapd_slot_get_connected_plugs` - `snapd_slot_ref_get_slot` - `snapd_slot_ref_get_snap` - `SNAPD_ERROR_OPTION_NOT_FOUND` - Deprecated API : - `snapd_client_get_interfaces_async` - `snapd_client_get_interfaces_finish` - `snapd_client_get_interfaces_sync` - `snapd_connection_get_name` - `snapd_connection_get_snap` - `snapd_plug_get_connections` - `snapd_slot_get_connections` - Allow searching via common-id - Add a description markdown parser - Replace `SnapdConnection` with `SnapdPlugRef` and `SnapdSlotRef` - Support updated connections API (`/v2/connections`) - Support updated `/v2/interfaces&select=` API - Support snap configuration API - Add Qt interface attribute API - Make `snapd_client_set_socket_path` revert to the default when `NULL` passed. - Fix C99 mode not being enabled on older versions of GCC Note that Tenable Network Security has extracted the preceding description block directly from the Fedora update system website. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues." ); script_set_attribute( attribute:"see_also", value:"https://bodhi.fedoraproject.org/updates/FEDORA-2019-bc3dfb389f" ); script_set_attribute( attribute:"solution", value:"Update the affected snapd-glib package." ); script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:N/I:P/A:N"); script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C"); script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"); script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C"); script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available"); script_set_attribute(attribute:"plugin_type", value:"local"); script_set_attribute(attribute:"cpe", value:"p-cpe:/a:fedoraproject:fedora:snapd-glib"); script_set_attribute(attribute:"cpe", value:"cpe:/o:fedoraproject:fedora:29"); script_set_attribute(attribute:"vuln_publication_date", value:"2019/04/24"); script_set_attribute(attribute:"patch_publication_date", value:"2019/07/13"); script_set_attribute(attribute:"plugin_publication_date", value:"2019/07/15"); script_set_attribute(attribute:"generated_plugin", value:"current"); script_end_attributes(); script_category(ACT_GATHER_INFO); script_copyright(english:"This script is Copyright (C) 2019-2020 and is owned by Tenable, Inc. or an Affiliate thereof."); script_family(english:"Fedora Local Security Checks"); script_dependencies("ssh_get_info.nasl"); script_require_keys("Host/local_checks_enabled", "Host/RedHat/release", "Host/RedHat/rpm-list"); exit(0); } include("audit.inc"); include("global_settings.inc"); include("rpm.inc"); if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED); release = get_kb_item("Host/RedHat/release"); if (isnull(release) || "Fedora" >!< release) audit(AUDIT_OS_NOT, "Fedora"); os_ver = pregmatch(pattern: "Fedora.*release ([0-9]+)", string:release); if (isnull(os_ver)) audit(AUDIT_UNKNOWN_APP_VER, "Fedora"); os_ver = os_ver[1]; if (! preg(pattern:"^29([^0-9]|$)", string:os_ver)) audit(AUDIT_OS_NOT, "Fedora 29", "Fedora " + os_ver); if (!get_kb_item("Host/RedHat/rpm-list")) audit(AUDIT_PACKAGE_LIST_MISSING); cpu = get_kb_item("Host/cpu"); if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH); if ("x86_64" >!< cpu && cpu !~ "^i[3-6]86$") audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, "Fedora", cpu); flag = 0; if (rpm_check(release:"FC29", reference:"snapd-glib-1.48-1.fc29")) flag++; if (flag) { security_report_v4( port : 0, severity : SECURITY_WARNING, extra : rpm_report_get() ); exit(0); } else { tested = pkg_tests_get(); if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested); else audit(AUDIT_PACKAGE_NOT_INSTALLED, "snapd-glib"); }
References
- http://www.openwall.com/lists/oss-security/2019/04/25/7
- http://www.openwall.com/lists/oss-security/2019/04/25/7
- https://github.com/snapcore/snapd/pull/6642
- https://github.com/snapcore/snapd/pull/6642
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6VACEKVQ7UAZ32WO4ZKCFW6YOBSYJ76L/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6VACEKVQ7UAZ32WO4ZKCFW6YOBSYJ76L/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VPU6APEZHAA7N2AI57OT4J2P7NKHFOLM/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VPU6APEZHAA7N2AI57OT4J2P7NKHFOLM/
- https://www.openwall.com/lists/oss-security/2019/04/18/4
- https://www.openwall.com/lists/oss-security/2019/04/18/4