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CVE-2023-26485
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CVE-2023-26485
MITRE ATT&CK
Collection
Command and Control
Credential Access
Defense Evasion
Discovery
Execution
Exfiltration
Impact
Initial Access
Lateral Movement
Persistence
Privilege Escalation
Topic Tags
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 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:
- Open an issue in github/cmark-gfm
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CVE ID
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