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)
Metrics
Affected Vendors & Products
References
History
Tue, 11 Feb 2025 18:15:00 +0000
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Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2025-02-11T17:20:37.921Z
Reserved: 2023-02-23T23:22:58.575Z
Link: CVE-2023-26485
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Updated: 2024-08-02T11:53:52.747Z
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Status : Modified
Published: 2023-03-31T23:15:07.250
Modified: 2024-11-21T07:51:36.963
Link: CVE-2023-26485
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