Vulnerability Details 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](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)
Exploit prediction scoring system (EPSS) score
EPSS Score 0.002
EPSS Ranking 37.3%
CVSS Severity
CVSS v3 Score 5.3
References
- https://github.com/github/cmark-gfm/commit/07a66c9bc341f902878e37d7da8647d6ef150987
- https://github.com/github/cmark-gfm/security/advisories/GHSA-r8vr-c48j-fcc5
- https://github.com/github/cmark-gfm/commit/07a66c9bc341f902878e37d7da8647d6ef150987
- https://github.com/github/cmark-gfm/security/advisories/GHSA-r8vr-c48j-fcc5
Products affected by CVE-2023-26485
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cpe:2.3:a:github:cmark-gfm:-
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cpe:2.3:a:github:cmark-gfm:0.27.1.gfm.0
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cpe:2.3:a:github:cmark-gfm:0.27.1.gfm.1
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cpe:2.3:a:github:cmark-gfm:0.27.1.gfm.2
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cpe:2.3:a:github:cmark-gfm:0.27.1.gfm.3
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cpe:2.3:a:github:cmark-gfm:0.27.1.gfm.4
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cpe:2.3:a:github:cmark-gfm:0.28.0.gfm.10
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cpe:2.3:a:github:cmark-gfm:0.28.0.gfm.11
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cpe:2.3:a:github:cmark-gfm:0.28.0.gfm.5
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cpe:2.3:a:github:cmark-gfm:0.28.0.gfm.6
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cpe:2.3:a:github:cmark-gfm:0.28.0.gfm.7
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cpe:2.3:a:github:cmark-gfm:0.28.0.gfm.8
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cpe:2.3:a:github:cmark-gfm:0.28.0.gfm.9
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cpe:2.3:a:github:cmark-gfm:0.28.3.gfm.12
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cpe:2.3:a:github:cmark-gfm:0.28.3.gfm.13
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cpe:2.3:a:github:cmark-gfm:0.28.3.gfm.14
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cpe:2.3:a:github:cmark-gfm:0.28.3.gfm.15
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cpe:2.3:a:github:cmark-gfm:0.28.3.gfm.16
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cpe:2.3:a:github:cmark-gfm:0.28.3.gfm.17
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cpe:2.3:a:github:cmark-gfm:0.28.3.gfm.18
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cpe:2.3:a:github:cmark-gfm:0.28.3.gfm.19
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cpe:2.3:a:github:cmark-gfm:0.28.3.gfm.20
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cpe:2.3:a:github:cmark-gfm:0.28.3.gfm.21
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cpe:2.3:a:github:cmark-gfm:0.29.0.gfm.0
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cpe:2.3:a:github:cmark-gfm:0.29.0.gfm.1
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cpe:2.3:a:github:cmark-gfm:0.29.0.gfm.2
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cpe:2.3:a:github:cmark-gfm:0.29.0.gfm.3
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cpe:2.3:a:github:cmark-gfm:0.29.0.gfm.4
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cpe:2.3:a:github:cmark-gfm:0.29.0.gfm.5
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cpe:2.3:a:github:cmark-gfm:0.29.0.gfm.6
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cpe:2.3:a:github:cmark-gfm:0.29.0.gfm.7
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cpe:2.3:a:github:cmark-gfm:0.29.0.gfm.8
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cpe:2.3:a:github:cmark-gfm:0.29.0.gfm.9