CVE-2020-7469

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ============================================================================= FreeBSD-SA-20:31.icmp6 Security Advisory The FreeBSD Project Topic: ICMPv6 use-after-free in error message handling Category: core Module: icmp6 Announced: 2020-12-01 Credits: Maxime Villard Affects: All supported versions of FreeBSD. Corrected: 2020-11-05 22:41:54 UTC (stable/12, 12.2-STABLE) 2020-12-01 19:38:52 UTC (releng/12.2, 12.2-RELEASE-p1) 2020-12-01 19:38:52 UTC (releng/12.1, 12.1-RELEASE-p11) 2020-12-01 03:07:26 UTC (stable/11, 11.4-STABLE) 2020-12-01 19:38:52 UTC (releng/11.4, 11.4-RELEASE-p5) CVE Name: CVE-2020-7469 For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit . I. Background ICMPv6 is the ICMP protocol for IPv6. It is used to transmit informational and error messages between IPv6 hosts. II. Problem Description When an ICMPv6 error message is received, the FreeBSD ICMPv6 stack may extract information from the message to hand to upper-layer protocols. As a part of this operation, it may parse IPv6 header options from a packet embedded in the ICMPv6 message. The handler for a routing option caches a pointer into the packet buffer holding the ICMPv6 message. However, when processing subsequent options the packet buffer may be freed, rendering the cached pointer invalid. The network stack may later dereference the pointer, potentially triggering a use-after-free. III. Impact A remote host may be able to trigger a read of freed kernel memory. This may trigger a kernel panic if the address had been unmapped. IV. Workaround Systems with IPv6 disabled are not affected. No workaround is available except to disable IPv6 on the system’s network interfaces. V. Solution Upgrade your vulnerable system to a supported FreeBSD stable or release / security branch (releng) dated after the correction date and reboot. Perform one of the following: 1) To update your vulnerable system via a binary patch: Systems running a RELEASE version of FreeBSD on the i386 or amd64 platforms can be updated via the freebsd-update(8) utility: # freebsd-update fetch # freebsd-update install # shutdown -r +10min “Rebooting for a security update” 2) To update your vulnerable system via a source code patch: The following patches have been verified to apply to the applicable FreeBSD release branches. a) Download the relevant patch from the location below, and verify the detached PGP signature using your PGP utility. [FreeBSD 12.2] # fetch https://security.FreeBSD.org/patches/SA-20:31/icmp6.12.2.patch # fetch https://security.FreeBSD.org/patches/SA-20:31/icmp6.12.2.patch.asc # gpg --verify icmp6.12.2.patch.asc [FreeBSD 12.1] # fetch https://security.FreeBSD.org/patches/SA-20:31/icmp6.12.1.patch # fetch https://security.FreeBSD.org/patches/SA-20:31/icmp6.12.1.patch.asc # gpg --verify icmp6.12.1.patch.asc [FreeBSD 11.4] # fetch https://security.FreeBSD.org/patches/SA-20:31/icmp6.11.4.patch # fetch https://security.FreeBSD.org/patches/SA-20:31/icmp6.11.4.patch.asc # gpg --verify icmp6.11.4.patch.asc b) Apply the patch. Execute the following commands as root: # cd /usr/src # patch < /path/to/patch c) Recompile your kernel as described in and reboot the system. VI. Correction details The following list contains the correction revision numbers for each affected branch. Branch/path Revision - ------------------------------------------------------------------------- stable/12/ r367402 releng/12.2/ r368255 releng/12.1/ r368255 stable/11/ r368202 releng/11.4/ r368255 - ------------------------------------------------------------------------- To see which files were modified by a particular revision, run the following command, replacing NNNNNN with the revision number, on a machine with Subversion installed: # svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base Or visit the following URL, replacing NNNNNN with the revision number: VII. References The latest revision of this advisory is available at -----BEGIN PGP SIGNATURE----- iQKTBAEBCgB9FiEE/A6HiuWv54gCjWNV05eS9J6n5cIFAl/GndVfFIAAAAAALgAo aXNzdWVyLWZwckBub3RhdGlvbnMub3BlbnBncC5maWZ0aGhvcnNlbWFuLm5ldEZD MEU4NzhBRTVBRkU3ODgwMjhENjM1NUQzOTc5MkY0OUVBN0U1QzIACgkQ05eS9J6n 5cIE8g//d4TXo4cXH4H0k6Et5lCoKz7R+x/wE6EuTymvKOiYyvwGwk3TZnLwhSSr +FmwYMa0nQfHl3JdbUFYcQdA8Q/mvh0OZf55icRRHwchA+V9ENzuN8DqP1FPbL09 Ar3Q7osE2LyblTX9vOF0KYNWT+OmUZE5BDHEJ+OD5TKV2xWMkrksVOylXdKKgNyK Umc3uccud3nvBlrIeP5SiNewCP06/SEZkSovFI1QKCVJGs4hCO97Es0RWiY9MkPG JcUOdCsYVrvfcWNeRkcAqnH/vgWQYBumSW15ldNGIrMaUAi0DiDTisFIifPI1z8T j+WmxN2IGvjYQzLBLhpJqq9Ox1OUD2R6Q0YSsndMHgf2bo1HheVUtQlBPMOq/V/8 I74Ppu2NPxdh2ocUzk60XaNZ2PuZhqkDMOLqZLcKNEe7m94ImzfNxtDGyRkEwpbw /Vu4ysFrHQR4derU3c9TV+LJwCYaoNw//0WKpcycnqfvb/y5dWgOc3sBf5zwiuRL NNwRnnRK/gaGoigJxm/Ev2SNsJDLs0g7IuscwYPRtadi1eUTeKeJFg3yvSVTYRov tGPIhWYmWvOmKSg8ZGIAnTcXeNleyymw+vi6l0gHtwcLJ0AjdbVEWZ3FCy7XvD3c yRbkJ4ORllto95caGGtzHDj0CMShYaOMNhrf+QrEYDRMB8jfXh0= =a0pv -----END PGP SIGNATURE-----