CVE-2023-26485

cmark-gfm is GitHub&amp;#39;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.<br /> <br /> <br /> <br /> <br /> ### Impact<br /> <br /> A polynomial time complexity issue in cmark-gfm may lead to unbounded resource exhaustion and subsequent denial of service.<br /> <br /> ### Proof of concept<br /> <br /> ```<br /> $ ~/cmark-gfm$ python3 -c &amp;#39;pad = "_" * 100000; print(pad + "." + pad, end="")&amp;#39; | time ./build/src/cmark-gfm --to plaintext<br /> ```<br /> <br /> Increasing the number 10000 in the above commands causes the running time to increase quadratically.<br /> <br /> ### Patches<br /> <br /> This vulnerability have been patched in 0.29.0.gfm.10.<br /> <br /> ### Note on cmark and cmark-gfm<br /> <br /> XXX: TBD<br /> <br /> [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`. <br /> <br /> ### Credit<br /> <br /> We would like to thank @gravypod for reporting this vulnerability.<br /> <br /> ### References<br /> <br /> https://en.wikipedia.org/wiki/Time_complexity<br /> <br /> ### For more information<br /> <br /> If you have any questions or comments about this advisory:<br /> <br /> * Open an issue in [github/cmark-gfm](https://github.com/github/cmark-gfm)<br />