Vulnerability Database

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Total vulnerabilities in the database

CVE-2023-26485

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:

  • Published: Apr 1, 2023
  • Updated: Nov 8, 2023
  • CVE: CVE-2023-26485
  • Severity: High
  • Exploit:

CVSS v3:

  • Severity: High
  • Score: 7.5
  • AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWEs:

Software From Fixed in
github / cmark-gfm - 0.29.0.gfm.10