Date: Wed, 30 Aug 2017 22:03:46 +0200 From: Salvatore Bonaccorso <carnil@...ian.org> To: OSS Security Mailinglist <oss-security@...ts.openwall.com> Cc: James Cowgill <jcowgill@...ian.org> Subject: mbed TLS: CVE-2017-14032: Bypass of authentication of peer possible when the authentication mode is configured as 'optional' Hi MITRE has assigned CVE-2017-14032 for the following issue in mbed TLS: https://tls.mbed.org/tech-updates/security-advisories/mbedtls-security-advisory-2017-02 > Title Bypass of authentication of peer possible when the authentication > mode is configured as 'optional' > Date 28th August 2017 > Affects All versions of mbed TLS from version 1.3.10 and up, including all > 2.1 and later releases > Not mbed TLS 1.3.9 and earlier > affected > Impact Use of the 'optional' authentication mode can permit the peer to > bypass peer authentication > Severity High > > Vulnerability > ------------- > If a malicious peer supplies an X.509 certificate chain that has more than > MBEDTLS_X509_MAX_INTERMEDIATE_CA intermediates (which by default is 8), it > could bypass authentication of the certificates, when the authentication mode > was set to 'optional' eg. MBEDTLS_SSL_VERIFY_OPTIONAL. The issue could be > triggered remotely by both the client and server sides. > > If the authentication mode, which can be set by the function > mbedtls_ssl_conf_authmode(), was set to 'required' eg. > MBEDTLS_SSL_VERIFY_REQUIRED which is the default, authentication would occur > normally as intended. > > Impact > ------ > Depending on the platform, an attack exploiting this vulnerability could allow > successful impersonation of the intended peer and permit man-in-the-middle > attacks. > > Resolution > ---------- > Affected users should upgrade to mbed TLS 1.3.21, mbed TLS 2.1.9 or mbed TLS > 2.6.0. > > Workaround > ---------- > Users should wherever possible upgrade to the newer version of mbed TLS. Where > this is not practical, users should consider if changing the authentication to > the 'required' mode MBEDTLS_SSL_VERIFY_REQUIRED is practical for their > application. References: - https://github.com/ARMmbed/mbedtls/commit/31458a18788b0cf0b722acda9bb2f2fe13a3fb32 - https://github.com/ARMmbed/mbedtls/commit/d15795acd5074e0b44e71f7ede8bdfe1b48591fc - https://bugs.debian.org/873557 Regards, Salvatore
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