CVE-2023-26485

Date: March 31, 2023

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)

Language: Ruby