During TLS 1.2 exchanges, handshake hashes are generated which point to a message buffer. This saved data is used for later messages but in some cases, the handshake transcript can exceed the space available in the current buffer, causing the allocation of a new buffer. This leaves a pointer pointing to the old, freed buffer, resulting in a use-after-free when handshake hashes are then calculated afterwards. This can result in a potentially exploitable crash. This vulnerability affects Firefox < 56, Firefox ESR < 52.4, and Thunderbird < 52.4.

References

• https://nvd.nist.gov/vuln/detail/CVE-2017-7805
• https://access.redhat.com/errata/RHSA-2017:2832
• https://bugzilla.mozilla.org/show_bug.cgi?id=1377618
• https://lists.debian.org/debian-lts-announce/2017/11/msg00000.html
• https://security.gentoo.org/glsa/201803-14
• https://www.debian.org/security/2017/dsa-3987
• https://www.debian.org/security/2017/dsa-3998
• https://www.debian.org/security/2017/dsa-4014
• https://www.mozilla.org/security/advisories/mfsa2017-21/
• https://www.mozilla.org/security/advisories/mfsa2017-22/
• https://www.mozilla.org/security/advisories/mfsa2017-23/
• http://www.oracle.com/technetwork/security-advisory/cpuoct2018-4428296.html
• http://www.securityfocus.com/bid/101059
• http://www.securitytracker.com/id/1039465