Vulnerabilities > CVE-2019-14859 - Improper Verification of Cryptographic Signature vulnerability in multiple products
Attack vector
NETWORK Attack complexity
LOW Privileges required
NONE Confidentiality impact
HIGH Integrity impact
HIGH Availability impact
NONE Summary
A flaw was found in all python-ecdsa versions before 0.13.3, where it did not correctly verify whether signatures used DER encoding. Without this verification, a malformed signature could be accepted, making the signature malleable. Without proper verification, an attacker could use a malleable signature to create false transactions.
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 SuSE Local Security Checks NASL id OPENSUSE-2019-2472.NASL description This update for python-ecdsa to version 0.13.3 fixes the following issues : Security issues fixed : - CVE-2019-14853: Fixed unexpected exceptions during signature decoding (bsc#1153165). - CVE-2019-14859: Fixed a signature malleability caused by insufficient checks of DER encoding (bsc#1154217). This update was imported from the SUSE:SLE-15:Update update project. last seen 2020-06-01 modified 2020-06-02 plugin id 130892 published 2019-11-12 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/130892 title openSUSE Security Update : python-ecdsa (openSUSE-2019-2472) code # # (C) Tenable Network Security, Inc. # # The descriptive text and package checks in this plugin were # extracted from openSUSE Security Update openSUSE-2019-2472. # # The text description of this plugin is (C) SUSE LLC. # include("compat.inc"); if (description) { script_id(130892); script_version("1.5"); script_cvs_date("Date: 2020/01/16"); script_cve_id("CVE-2019-14853", "CVE-2019-14859"); script_name(english:"openSUSE Security Update : python-ecdsa (openSUSE-2019-2472)"); script_summary(english:"Check for the openSUSE-2019-2472 patch"); script_set_attribute( attribute:"synopsis", value:"The remote openSUSE host is missing a security update." ); script_set_attribute( attribute:"description", value: "This update for python-ecdsa to version 0.13.3 fixes the following issues : Security issues fixed : - CVE-2019-14853: Fixed unexpected exceptions during signature decoding (bsc#1153165). - CVE-2019-14859: Fixed a signature malleability caused by insufficient checks of DER encoding (bsc#1154217). This update was imported from the SUSE:SLE-15:Update update project." ); script_set_attribute( attribute:"see_also", value:"https://bugzilla.opensuse.org/show_bug.cgi?id=1153165" ); script_set_attribute( attribute:"see_also", value:"https://bugzilla.opensuse.org/show_bug.cgi?id=1154217" ); script_set_attribute( attribute:"solution", value:"Update the affected python-ecdsa packages." ); script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:P/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:H/I:H/A:N"); script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C"); script_set_attribute(attribute:"cvss_score_source", value:"CVE-2019-14859"); 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:novell:opensuse:python2-ecdsa"); script_set_attribute(attribute:"cpe", value:"p-cpe:/a:novell:opensuse:python3-ecdsa"); script_set_attribute(attribute:"cpe", value:"cpe:/o:novell:opensuse:15.0"); script_set_attribute(attribute:"vuln_publication_date", value:"2019/11/26"); script_set_attribute(attribute:"patch_publication_date", value:"2019/11/09"); script_set_attribute(attribute:"plugin_publication_date", value:"2019/11/12"); 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:"SuSE Local Security Checks"); script_dependencies("ssh_get_info.nasl"); script_require_keys("Host/local_checks_enabled", "Host/SuSE/release", "Host/SuSE/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/SuSE/release"); if (isnull(release) || release =~ "^(SLED|SLES)") audit(AUDIT_OS_NOT, "openSUSE"); if (release !~ "^(SUSE15\.0)$") audit(AUDIT_OS_RELEASE_NOT, "openSUSE", "15.0", release); if (!get_kb_item("Host/SuSE/rpm-list")) audit(AUDIT_PACKAGE_LIST_MISSING); flag = 0; if ( rpm_check(release:"SUSE15.0", reference:"python2-ecdsa-0.13.3-lp150.2.3.1") ) flag++; if ( rpm_check(release:"SUSE15.0", reference:"python3-ecdsa-0.13.3-lp150.2.3.1") ) flag++; if (flag) { if (report_verbosity > 0) security_warning(port:0, extra:rpm_report_get()); else security_warning(0); exit(0); } else { tested = pkg_tests_get(); if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested); else audit(AUDIT_PACKAGE_NOT_INSTALLED, "python2-ecdsa / python3-ecdsa"); }
NASL family SuSE Local Security Checks NASL id OPENSUSE-2019-2474.NASL description This update for python-ecdsa to version 0.13.3 fixes the following issues : Security issues fixed : - CVE-2019-14853: Fixed unexpected exceptions during signature decoding (bsc#1153165). - CVE-2019-14859: Fixed a signature malleability caused by insufficient checks of DER encoding (bsc#1154217). This update was imported from the SUSE:SLE-15:Update update project. last seen 2020-06-01 modified 2020-06-02 plugin id 130893 published 2019-11-12 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/130893 title openSUSE Security Update : python-ecdsa (openSUSE-2019-2474) NASL family Debian Local Security Checks NASL id DEBIAN_DSA-4588.NASL description It was discovered that python-ecdsa, a cryptographic signature library for Python, incorrectly handled certain signatures. A remote attacker could use this issue to cause python-ecdsa to either not warn about incorrect signatures, or generate exceptions resulting in a denial-of-service. last seen 2020-06-01 modified 2020-06-02 plugin id 132110 published 2019-12-18 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/132110 title Debian DSA-4588-1 : python-ecdsa - security update NASL family Debian Local Security Checks NASL id DEBIAN_DLA-1978.NASL description It was discovered that python-ecdsa, a cryptographic signature library for Python, did not correctly verify DER encoded signatures. Malformed signatures could lead to unexpected exceptions and in some cases did not raise any exception. For Debian 8 last seen 2020-06-01 modified 2020-06-02 plugin id 130407 published 2019-10-31 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/130407 title Debian DLA-1978-1 : python-ecdsa security update NASL family Ubuntu Local Security Checks NASL id UBUNTU_USN-4196-1.NASL description It was discovered that python-ecdsa incorrectly handled certain signatures. A remote attacker could possibly use this issue to cause python-ecdsa to generate unexpected exceptions, resulting in a denial of service. (CVE-2019-14853) It was discovered that python-ecdsa incorrectly verified DER encoding in signatures. A remote attacker could use this issue to perform certain malleability attacks. (CVE-2019-14859). Note that Tenable Network Security has extracted the preceding description block directly from the Ubuntu security advisory. 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 131162 published 2019-11-20 reporter Ubuntu Security Notice (C) 2019-2020 Canonical, Inc. / NASL script (C) 2019-2020 and is owned by Tenable, Inc. or an Affiliate thereof. source https://www.tenable.com/plugins/nessus/131162 title Ubuntu 16.04 LTS / 18.04 LTS / 19.04 / 19.10 : python-ecdsa vulnerabilities (USN-4196-1)
References
- https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2019-14859
- https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2019-14859
- https://github.com/warner/python-ecdsa/issues/114
- https://github.com/warner/python-ecdsa/issues/114
- https://github.com/warner/python-ecdsa/releases/tag/python-ecdsa-0.13.3
- https://github.com/warner/python-ecdsa/releases/tag/python-ecdsa-0.13.3
- https://pypi.org/project/ecdsa/0.13.3/
- https://pypi.org/project/ecdsa/0.13.3/