Vulnerability 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)
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Github | Cmark-Gfm | < 0.29.0.gfm.10 |
Related Weaknesses (CWE)
References
- https://github.com/github/cmark-gfm/commit/07a66c9bc341f902878e37d7da8647d6ef150Patch
- https://github.com/github/cmark-gfm/security/advisories/GHSA-r8vr-c48j-fcc5ExploitVendor Advisory
- https://github.com/github/cmark-gfm/commit/07a66c9bc341f902878e37d7da8647d6ef150Patch
- https://github.com/github/cmark-gfm/security/advisories/GHSA-r8vr-c48j-fcc5ExploitVendor Advisory
FAQ
What is CVE-2023-26485?
CVE-2023-26485 is a vulnerability with a CVSS score of 5.3 (MEDIUM). 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 subseque...
How severe is CVE-2023-26485?
CVE-2023-26485 has been rated MEDIUM with a CVSS base score of 5.3/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2023-26485?
Check the references section above for vendor advisories and patch information. Affected products include: Github Cmark-Gfm.