Headline

CVE-2023-24824: Quadratic complexity bugs may lead to a denial of service

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 > or - 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.

2 years ago

CVE

Open in Source

#vulnerability #dos #git

Impact

Two polynomial time complexity issues in cmark-gfm may lead to unbounded resource exhaustion and subsequent denial of service.

Proof of concept

Issue 1:

python3 -c 'n = 10000; print(">"*n + "a*"*n)' | cmark-gfm

Issue 2:

python3 -c 'n = 10000; print(" -" * n + “x” + “\n” * n)' | cmark-gfm

Increasing the number 10000 in the above commands causes the running time to increase quadratically.

Patches

These vulnerabilities have been patched in 0.29.0.gfm.10.

Note on cmark and cmark-gfm

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 @nwellnhof for reporting the first vulnerability (issue 1). Issue 2 was subsequently found by GitHub Security Lab.

References

https://en.wikipedia.org/wiki/Time_complexity

For more information

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