FreeBSD Security Advisory FreeBSD-SA-20:18.posix_spawnp
8 July, 2020 by email@example.com | freebsd
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ============================================================================= FreeBSD-SA-20:18.posix_spawnp Security Advisory The FreeBSD Project Topic: posix_spawnp(3) buffer overflow Category: core Module: libc Announced: 2020-07-08 Credits: Andrew Gierth Affects: FreeBSD 11.4 Corrected: 2020-06-17 16:22:08 UTC (stable/12, 12.1-STABLE) 2020-06-17 16:22:08 UTC (stable/11, 11.4-STABLE) 2020-07-08 20:08:05 UTC (releng/11.4, 11.4-RELEASE-p1) CVE Name: CVE-2020-7458 Note: This vulnerability was introduced after the release of FreeBSD 11.3 and FreeBSD 12.1; FreeBSD 11.4 is the only affected release. 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 posix_spawnp(3) is a lightweight process creation mechanism provided by libc for general application usage. II. Problem Description posix_spawnp spawns a new thread with a limited stack allocated on the heap before delegating to execvp for the final execution within that thread. execvp would previously make unbounded allocations on the stack, directly proportional to the length of the user-controlled PATH environment variable. III. Impact Long values in the user-controlled PATH environment variable cause posix_spawnp to write beyond the end of stack that was allocated, ultimately overflowing the heap-allocated stack with a direct copy of the value stored in PATH. IV. Workaround No workaround is available. Few applications in the base system use posix_spawnp(3) and none of them are particularly viable candidates for an exploit. Use by third-party applications has not been investigated. 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 11.4] # fetch https://security.FreeBSD.org/patches/SA-20:18/posix_spawnp.patch # fetch https://security.FreeBSD.org/patches/SA-20:18/posix_spawnp.patch.asc # gpg --verify posix_spawnp.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 all daemons that use the library, or reboot the system. VI. Correction details The following list contains the correction revision numbers for each affected branch. Branch/path Revision - ------------------------------------------------------------------------- stable/12/ r362281 stable/11/ r362281 releng/11.4/ r363025 - ------------------------------------------------------------------------- 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-2020-7458> The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-20:18.posix_spawnp.asc> -----BEGIN PGP SIGNATURE----- iQKTBAEBCgB9FiEE/A6HiuWv54gCjWNV05eS9J6n5cIFAl8GLlNfFIAAAAAALgAo aXNzdWVyLWZwckBub3RhdGlvbnMub3BlbnBncC5maWZ0aGhvcnNlbWFuLm5ldEZD MEU4NzhBRTVBRkU3ODgwMjhENjM1NUQzOTc5MkY0OUVBN0U1QzIACgkQ05eS9J6n 5cLdthAAgchE9dOcTvmFerK/SEAI7G/+3l1GRQ/hKJfvGbvNuZKKudpMdCmLHzil MepCvRO7ft6OTBF66PaAscbdadD54CluQGjD96eLNnQ6dMgU5yZdWTUvvjdJze1R 200oAlAu2eoZvuRghSNFqh4s8iffYN/T4Tc1ubRCAyZUXYbq5rg3r21P9FugXX+Y RZhYzUNRMCi4ZSGkUmcqLltZZtSrI9GOU2H4cKpedYaHJ+b76tALt1fCsSVZwMJK 7WKiqKkw4ilRH5gbUuTqngVjt7Uy9JGyS2WrAwhnxLIr6+4qxAkiOltwZdFNUhSJ HGvTzl2As/gxxjqpqmvzegKfrGOd4pz2i7ZdAhhPWEK0sHNp1NttPQ7wWnU1Ikt3 bkoiy+eJTF43GL7IpxurOOMDdH9MWL/RAZBZNpTof4XCjhEHvvMaSoeO/GLpcSja +dYFoip65b1tlBtGt/tlgHVqlzCD86o6pBiRdZ7mYYLTxurDc/dcTpebypQPogcB agD3IO0hMXnt1Q/UQVl1pC3LDnSvabeHVI7xuB1T9UP/CsAxTt1nhEM4b9/YnJv5 Bt1cZFlBvZgrVFVvegYAf7lVz3TsF3xz2pKZD6wxezAk+QbH4ho6aTHWJkRotE4z C5bcIEbIz6OX+J7VjOxcgkTu+bFykWb9xcTjtKpRexxICMOef+E=2OBY -----END PGP SIGNATURE----- _______________________________________________ firstname.lastname@example.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-announce To unsubscribe, send any mail to "email@example.com"