CVE-2023-26485 Information

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 is a fork of 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

Reference

https://github.com/github/cmark-gfm/security/advisories/GHSA-r8vr-c48j-fcc5 https://github.com/github/cmark-gfm/commit/07a66c9bc341f902878e37d7da8647d6ef150987