CVE-2023-26485

Name	CVE-2023-26485
Description	cmark-gfm is GitHub's fork of cmark, a CommonMark parsing and rendering library and program in C. A polynomial time complexity issue in cmark-gfm may lead to unbounded resource exhaustion and subsequent denial of service. This CVE covers quadratic complexity issues when parsing text which leads with either large numbers of `_` characters. This issue has been addressed in version 0.29.0.gfm.10. Users are advised to upgrade. Users unable to upgrade should validate that their input comes from trusted sources. ### Impact A polynomial time complexity issue in cmark-gfm may lead to unbounded resource exhaustion and subsequent denial of service. ### Proof of concept ``` $ ~/cmark-gfm$ python3 -c 'pad = "_" * 100000; print(pad + "." + pad, end="")' \| time ./build/src/cmark-gfm --to plaintext ``` Increasing the number 10000 in the above commands causes the running time to increase quadratically. ### Patches This vulnerability have been patched in 0.29.0.gfm.10. ### Note on cmark and cmark-gfm XXX: TBD [cmark-gfm](https://github.com/github/cmark-gfm) is a fork of [cmark](https://github.com/commonmark/cmark) that adds the GitHub Flavored Markdown extensions. The two codebases have diverged over time, but share a common core. These bugs affect both `cmark` and `cmark-gfm`. ### Credit We would like to thank @gravypod for reporting this vulnerability. ### References https://en.wikipedia.org/wiki/Time_complexity ### For more information If you have any questions or comments about this advisory: * Open an issue in [github/cmark-gfm](https://github.com/github/cmark-gfm)
Source	CVE (at NVD; CERT, LWN, oss-sec, fulldisc, bugtraq, EDB, Metasploit, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, Mageia, GitHub advisories/code/issues, web search, more)
Debian Bugs	1034171, 1034172, 1034173, 1034174

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
cmark-gfm (PTS)	buster	0.28.3.gfm.19-3	vulnerable
	bullseye	0.29.0.gfm.0-6	vulnerable
	bookworm, sid	0.29.0.gfm.6-6	vulnerable
python-cmarkgfm (PTS)	buster, bullseye	0.4.2-1	vulnerable
	bookworm, sid	0.8.0-3	vulnerable
r-cran-commonmark (PTS)	buster	1.7-1	vulnerable
	bullseye	1.7-2	vulnerable
	bookworm, sid	1.8.1-1	vulnerable
ruby-commonmarker (PTS)	buster	0.17.9-1	vulnerable
	bullseye	0.21.0-1	vulnerable
	bookworm, sid	0.23.6-1	vulnerable

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Debian Bugs
cmark-gfm	source	(unstable)	(unfixed)	1034171
python-cmarkgfm	source	(unstable)	(unfixed)	1034172
r-cran-commonmark	source	(unstable)	(unfixed)	1034173
ruby-commonmarker	source	(unstable)	(unfixed)	1034174

Notes

[bookworm] - cmark-gfm <no-dsa> (Minor issue)
[bullseye] - cmark-gfm <no-dsa> (Minor issue)
[buster] - cmark-gfm <no-dsa> (Minor issue)
[bookworm] - python-cmarkgfm <no-dsa> (Minor issue)
[bullseye] - python-cmarkgfm <no-dsa> (Minor issue)
[buster] - python-cmarkgfm <no-dsa> (Minor issue)
[bookworm] - r-cran-commonmark <no-dsa> (Minor issue)
[bullseye] - r-cran-commonmark <no-dsa> (Minor issue)
[buster] - r-cran-commonmark <no-dsa> (Minor issue)
[bookworm] - ruby-commonmarker <no-dsa> (Minor issue)
[bullseye] - ruby-commonmarker <no-dsa> (Minor issue)
[buster] - ruby-commonmarker <no-dsa> (Minor issue)
https://github.com/github/cmark-gfm/security/advisories/GHSA-r8vr-c48j-fcc5
https://github.com/github/cmark-gfm/commit/07a66c9bc341f902878e37d7da8647d6ef150987 (0.29.0.gfm.10)