7.5

CVE-2023-26485

Exploit

Quadratic complexity may lead to a denial of service in cmark-gfm

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)
Daten sind bereitgestellt durch National Vulnerability Database (NVD)
Github ≫ Cmark-gfm Version < 0.29.0.gfm.10
Zu dieser CVE wurde keine Warnung gefunden.
EPSS Metriken
Typ Quelle Score Percentile
EPSS FIRST.org 1.03% 0.592
CVSS Metriken
Quelle Base Score Exploit Score Impact Score Vector String
nvd@nist.gov 7.5 3.9 3.6
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
security-advisories@github.com 5.3 3.9 1.4
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CWE-400 Uncontrolled Resource Consumption

The product does not properly control the allocation and maintenance of a limited resource.

CWE-407 Inefficient Algorithmic Complexity

An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.

https://github.com/github/cmark-gfm/commit/07a66c9bc341f902878e37d7da8647d6ef150987
Patch
https://github.com/github/cmark-gfm/security/advisories/GHSA-r8vr-c48j-fcc5
Vendor Advisory
Exploit