FreeBSD Security Advisory FreeBSD-SA-20:32.rtsold
1 December, 2020 by firstname.lastname@example.org | freebsd
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ============================================================================= FreeBSD-SA-20:32.rtsold Security Advisory The FreeBSD Project Topic: Multiple vulnerabilities in rtsold Category: core Module: rtsold Announced: 2020-12-01 Credits: Quarkslab Vulnerability Reports Affects: All supported versions of FreeBSD Corrected: 2020-12-01 19:35:48 UTC (stable/12, 12.2-STABLE) 2020-12-01 19:39:44 UTC (releng/12.2, 12.2-RELEASE-p1) 2020-12-01 19:39:44 UTC (releng/12.1, 12.1-RELEASE-p11) 2020-12-01 19:36:37 UTC (stable/11, 11.4-STABLE) 2020-12-01 19:39:44 UTC (releng/11.4, 11.4-RELEASE-p5) CVE Name: CVE-2020-25577 For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit <URL:https://security.FreeBSD.org/>. I. Background As part of the stateless address autoconfiguration (SLAAC) mechanism, IPv6 routers periodically broadcast router advertisement messages on attached networks to inform hosts of the correct network prefix, router address and MTU, as well as additional network parameters such as the DNS servers (RDNSS), DNS search list (DNSSL) and whether a stateful configuration service is available. Hosts that have recently joined the network can broadcast a router solicitation message to solicit an immediate advertisement instead of waiting for the next periodic advertisement. The router solicitation daemon, rtsold(8), broadcasts router solicitation messages at startup or when the state of an interface changes from passive to active. Incoming router advertisement messages are first processed by the kernel and then passed on to rtsold(8), which handles the DNS and stateful configuration options. II. Problem Description Two bugs exist in rtsold(8)'s RDNSS and DNSSL option handling. First, rtsold(8) failed to perform sufficient bounds checking on the extent of the option. In particular, it does not verify that the option does not extend past the end of the received packet before processing its contents. The kernel currently ignores such malformed packets but still passes them to userspace programs. Second, when processing a DNSSL option, rtsold(8) decodes domain name labels per an encoding specified in RFC 1035 in which the first octet of each label contains the label's length. rtsold(8) did not validate label lengths correctly and could overflow the destination buffer. III. Impact It is believed that these bugs could be exploited to gain remote code execution within the rtsold(8) daemon, which runs as root. Note that rtsold(8) only processes messages received from hosts attached to the same physical link as the interface(s) on which rtsold(8) is listening. In FreeBSD 12.2 rtsold(8) runs in a Capsicum sandbox, limiting the scope of a compromised rtsold(8) process. IV. Workaround No workaround is available, but systems that do not run rtsold(8) are not affected. V. Solution Upgrade your vulnerable system to a supported FreeBSD stable or release / security branch (releng) dated after the correction date. 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 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. # fetch https://security.FreeBSD.org/patches/SA-20:32/rtsold.patch # fetch https://security.FreeBSD.org/patches/SA-20:32/rtsold.patch.asc # gpg --verify rtsold.patch.asc b) Apply the patch. Execute the following commands as root: # cd /usr/src # patch < /path/to/patch c) Recompile the operating system using buildworld and installworld as described in <URL:https://www.FreeBSD.org/handbook/makeworld.html>. Restart the applicable daemons, or reboot the system. VI. Correction details The following list contains the correction revision numbers for each affected branch. Branch/path Revision - ------------------------------------------------------------------------- stable/12/ r368250 releng/12.2/ r368256 releng/12.1/ r368256 stable/11/ r368253 releng/11.4/ r368256 - ------------------------------------------------------------------------- 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: <URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN> VII. References <URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-25577> The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-20:32.rtsold.asc> -----BEGIN PGP SIGNATURE----- iQKTBAEBCgB9FiEE/A6HiuWv54gCjWNV05eS9J6n5cIFAl/GndZfFIAAAAAALgAo aXNzdWVyLWZwckBub3RhdGlvbnMub3BlbnBncC5maWZ0aGhvcnNlbWFuLm5ldEZD MEU4NzhBRTVBRkU3ODgwMjhENjM1NUQzOTc5MkY0OUVBN0U1QzIACgkQ05eS9J6n 5cIUXQ/+K/FAB22beBBiOUDaRMF0n4a/umwvwX2BAy7PsLIzRcYL8ydhvTWPXQnU KssmRoi0eobczpIYgIqTDNDTI46UErEvfoCBTIiY+uedER77FKxesfnO/9S3owvh 8uP+WCMzZXRfNvIYqEsK43ipm3LL4rDfUNLEdeFj0bLlwEwiTJaXsdLayJ3KpanN A3ykePDXnQD41BcDcotvzSV6r7o5dbCILI4K4zEOSCAXBP1Du16J/K/aHOWahJ20 Ex6YFg0llH3VkAVE9iGdHLGFqakjobUhm+LzV9ShAkXZqZs3Hx+p8dfM4w7aicCM f6Nn0rLlb4ZdSmMnbsexoZZwO0v2dQNHd1EEtQD6zjJfey1auJKJLTcLoWXH+3mm w5eOjjmqdOkab0h224q8jidhgyUm1c8By5H5aZ79y5SpRG0mfuS82Z6uIAf0KKZ3 uIzPswc0YtI30M638ZCKCug3gxwZu4EG7P08/Ab4B0fpyfqqLy6KVsMdH6w64R6+ 64twgiVPuM3DpokvTfdcQLp13IHeMJwkpdc/SICyg3NDAFJZMcIe6eqjko5FsNnH RSjA0SHRKyl303OLR+jUHe64m+LISyNne+fC1VoThbqQ1f5nWX9PlF4VjRu30Wz4 8VcmRCehMT1G1aIEGG74zKDeWDP6+bGeieBU7Pa/jfr/aI88Hw0=5tIC -----END PGP SIGNATURE----- _______________________________________________ email@example.com mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-announce To unsubscribe, send any mail to "firstname.lastname@example.org"