Vulnerabilities > CVE-2019-1728 - Improper Verification of Cryptographic Signature vulnerability in Cisco Nx-Os
Attack vector
LOCAL Attack complexity
LOW Privileges required
HIGH Confidentiality impact
HIGH Integrity impact
HIGH Availability impact
HIGH Summary
A vulnerability in the Secure Configuration Validation functionality of Cisco FXOS Software and Cisco NX-OS Software could allow an authenticated, local attacker to run arbitrary commands at system boot time with the privileges of root. The vulnerability is due to a lack of proper validation of system files when the persistent configuration information is read from the file system. An attacker could exploit this vulnerability by authenticating to the device and overwriting the persistent configuration storage with malicious executable files. An exploit could allow the attacker to run arbitrary commands at system startup and those commands will run as the root user. The attacker must have valid administrative credentials for the device.
Vulnerable Configurations
Common Weakness Enumeration (CWE)
Common Attack Pattern Enumeration and Classification (CAPEC)
- Padding Oracle Crypto Attack An attacker is able to efficiently decrypt data without knowing the decryption key if a target system leaks data on whether or not a padding error happened while decrypting the ciphertext. A target system that leaks this type of information becomes the padding oracle and an attacker is able to make use of that oracle to efficiently decrypt data without knowing the decryption key by issuing on average 128*b calls to the padding oracle (where b is the number of bytes in the ciphertext block). In addition to performing decryption, an attacker is also able to produce valid ciphertexts (i.e., perform encryption) by using the padding oracle, all without knowing the encryption key. Any cryptosystem can be vulnerable to padding oracle attacks if the encrypted messages are not authenticated to ensure their validity prior to decryption, and then the information about padding error is leaked to the attacker. This attack technique may be used, for instance, to break CAPTCHA systems or decrypt/modify state information stored in client side objects (e.g., hidden fields or cookies). This attack technique is a side-channel attack on the cryptosystem that uses a data leak from an improperly implemented decryption routine to completely subvert the cryptosystem. The one bit of information that tells the attacker whether a padding error during decryption has occurred, in whatever form it comes, is sufficient for the attacker to break the cryptosystem. That bit of information can come in a form of an explicit error message about a padding error, a returned blank page, or even the server taking longer to respond (a timing attack). This attack can be launched cross domain where an attacker is able to use cross-domain information leaks to get the bits of information from the padding oracle from a target system / service with which the victim is communicating. To do so an attacker sends a request containing ciphertext to the target system. Due to the browser's same origin policy, the attacker is not able to see the response directly, but can use cross-domain information leak techniques to still get the information needed (i.e., information on whether or not a padding error has occurred). For instance, this can be done using "img" tag plus the onerror()/onload() events. The attacker's JavaScript can make web browsers to load an image on the target site, and know if the image is loaded or not. This is 1-bit information needed for the padding oracle attack to work: if the image is loaded, then it is valid padding, otherwise it is not.
Nessus
NASL family CISCO NASL id CISCO-SA-20190515-FXOS-CONF-BYPASS.NASL description According to its self-reported version, Cisco FXOS Software is affected by a configuration bypass vulnerability due to a lack of proper validation of system files when the persistent configuration information is read from the file system. An authenticated, local attacker can exploit this, by authenticating to the device and overwriting the persistent configuration storage with malicious executable files. An exploit allows the attacker to run arbitrary commands at system startup with root privileges. Please see the included Cisco BIDs and Cisco Security Advisory for more information last seen 2020-04-16 modified 2020-01-09 plugin id 132720 published 2020-01-09 reporter This script is Copyright (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof. source https://www.tenable.com/plugins/nessus/132720 title Cisco FXOS Software Secure Configuration Bypass (cisco-sa-20190515-nxos-conf-bypass) code #TRUSTED 76048802073c8d18a1b71c5237e83817ae124ad8018b0f48c74fa2b03d5123701a78e566fb8aebf1b8867a8516e0ecd8109a03f2660b84f0e27c894d35eaa6d4b83e5b0eb34f9a1c696d9b554983e30afa11177f24ec6d8961a9fe301bbe671bb378dbcfcd7e2ffccd07004ac84a34c3f4ba569263a2c59d85a59629c6564c962c40a49f9e138ebf2854e9fc922b8969d33786648a92ea42f330c567f9863349e894857b7529cd2f0d07462152c469a73ef22db0e692da0dddb1281c92cddace67c39d5fd8cc3b3702789775acea9b48c011f1d48b94acb860f8a67c10fddfc1236b0bac0c7286fae102f967380c0a8852b391069f8927d316d07bddc4c10de8c432cb31734c9dd110f001b16de8763aefbec5c0444a586137b34bbf23e334501c96e040357b46e9348d6fc1b88cea734582ba272d6dfcdae21436ae3e20b05d6e41dde4c28f298db1331491270679054ccdda0bcd29318c3ade345ec29695d3f0572e6b499b08c4c7aca5677f4cd02ce6706779d3d35f6982259a540382dcc769d23316e31219ea4f5e34817c1a0a5602eb61b7aa4d1d7df13ff0a9a8513ff40dcb0a76c2cc5ead9c7381a0d4ba145c0cd873ef455a4dbae2805066947dcd8923f5474bcf780217df51e87eaba1b4233530c1f759fb96123f36df38fda6eef024329fa1af1e0ee3e4583101f35036d586fa59843df05e2c781fa2016cab002b # # (C) Tenable Network Security, Inc. # include('compat.inc'); if (description) { script_id(132720); script_version("1.6"); script_set_attribute(attribute:"plugin_modification_date", value:"2020/04/16"); script_cve_id("CVE-2019-1728"); script_bugtraq_id(108391); script_xref(name:"CISCO-BUG-ID", value:"CSCvi96584"); script_xref(name:"CISCO-SA", value:"cisco-sa-20190515-nxos-conf-bypass"); script_xref(name:"IAVA", value:"2019-A-0173"); script_name(english:"Cisco FXOS Software Secure Configuration Bypass (cisco-sa-20190515-nxos-conf-bypass)"); script_set_attribute(attribute:"synopsis", value: "The remote device is missing a vendor-supplied security patch"); script_set_attribute(attribute:"description", value: "According to its self-reported version, Cisco FXOS Software is affected by a configuration bypass vulnerability due to a lack of proper validation of system files when the persistent configuration information is read from the file system. An authenticated, local attacker can exploit this, by authenticating to the device and overwriting the persistent configuration storage with malicious executable files. An exploit allows the attacker to run arbitrary commands at system startup with root privileges. Please see the included Cisco BIDs and Cisco Security Advisory for more information"); # https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190515-nxos-conf-bypass script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?1a24f9c8"); script_set_attribute(attribute:"see_also", value:"https://bst.cloudapps.cisco.com/bugsearch/bug/CSCvi96584"); script_set_attribute(attribute:"solution", value: "Upgrade to the relevant fixed version referenced in Cisco bug IDs CSCvi96584."); script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:N/C:C/I:C/A:C"); script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C"); script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H"); script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C"); script_set_attribute(attribute:"cvss_score_source", value:"CVE-2019-1728"); script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available"); script_set_attribute(attribute:"vuln_publication_date", value:"2019/05/15"); script_set_attribute(attribute:"patch_publication_date", value:"2019/05/15"); script_set_attribute(attribute:"plugin_publication_date", value:"2020/01/09"); script_set_attribute(attribute:"plugin_type", value:"local"); script_set_attribute(attribute:"cpe", value:"cpe:/o:cisco:fxos"); script_set_attribute(attribute:"stig_severity", value:"I"); script_end_attributes(); script_category(ACT_GATHER_INFO); script_family(english:"CISCO"); script_copyright(english:"This script is Copyright (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof."); script_dependencies("cisco_enumerate_firepower.nbin", "cisco_asa_firepower_version.nasl"); script_require_keys("installed_sw/FXOS"); exit(0); } include('vcf.inc'); include('audit.inc'); include('cisco_workarounds.inc'); include('ccf.inc'); app_info = vcf::get_app_info(app:'FXOS'); product_info = make_array('model' , app_info['Model'], 'version' , app_info['version'], 'name', 'FXOS'); if( isnull(product_info['model']) || product_info['model'] !~ "^(41|93)[0-9]{2}$" ) audit(AUDIT_HOST_NOT, 'affected'); vuln_ranges = [ {'min_ver' : '0.0', 'fix_ver': '2.4.1.101'} ]; workarounds = make_list(CISCO_WORKAROUNDS['no_workaround']); workaround_params = make_list(); reporting = make_array( 'port' , 0, 'severity' , SECURITY_HOLE, 'version' , product_info['version'], 'bug_id' , 'CSCvi96584' ); cisco::check_and_report( product_info:product_info, workarounds:workarounds, workaround_params:workaround_params, reporting:reporting, vuln_ranges:vuln_ranges );NASL family CISCO NASL id CISCO-SA-20190515-NXOS-CONF-BYPASS.NASL description According to its self-reported version, Cisco NX-OS Software is affected by a configuration bypass vulnerability due to a lack of proper validation of system files when the persistent configuration information is read from the file system. An authenticated, local attacker can exploit this, by authenticating to the device and overwriting the persistent configuration storage with malicious executable files. An exploit allows the attacker to run arbitrary commands at system startup with root privileges. Please see the included Cisco BIDs and Cisco Security Advisory for more information last seen 2020-06-01 modified 2020-06-02 plugin id 132719 published 2020-01-09 reporter This script is Copyright (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof. source https://www.tenable.com/plugins/nessus/132719 title Cisco NX-OS Software Secure Configuration Bypass (cisco-sa-20190515-nxos-conf-bypass)