| Name | CVE-2020-24240 |
| Description | GNU Bison before 3.7.1 has a use-after-free in _obstack_free in lib/obstack.c (called from gram_lex) when a '\0' byte is encountered. NOTE: there is a risk only if Bison is used with untrusted input, and the observed bug happens to cause unsafe behavior with a specific compiler/architecture. The bug report was intended to show that a crash may occur in Bison itself, not that a crash may occur in code that is generated by Bison. |
| Source | CVE (at NVD; CERT, LWN, oss-sec, fulldisc, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more) |
Vulnerable and fixed packages
The table below lists information on source packages.
| Source Package | Release | Version | Status |
|---|
| bison (PTS) | jessie | 2:3.0.2.dfsg-2 | vulnerable |
| stretch | 2:3.0.4.dfsg-1 | fixed |
| buster | 2:3.3.2.dfsg-1 | fixed |
| bullseye | 2:3.7.5+dfsg-1 | fixed |
| sid, trixie, bookworm | 2:3.8.2+dfsg-1 | fixed |
The information below is based on the following data on fixed versions.
| Package | Type | Release | Fixed Version | Urgency | Origin | Debian Bugs |
|---|
| bison | source | stretch | (not affected) | | | |
| bison | source | buster | (not affected) | | | |
| bison | source | (unstable) | 2:3.7.2+dfsg-1 | unimportant | | |
Notes
[buster] - bison <not-affected> (Vulnerable code introduced later)
[stretch] - bison <not-affected> (Vulnerable code introduced later)
Introduced by: https://github.com/akimd/bison/commit/7346163840080f289f0adbadfbf5659c620d5fea (v3.5.91)
Fixed by: https://github.com/akimd/bison/commit/be95a4fe2951374676efc9454ffee8638faaf68d (v3.7.1)
https://lists.gnu.org/r/bug-bison/2020-07/msg00051.html
Crash in CLI tool, no security impact