CVE-2023-26485 Quadratic complexity may lead to a denial of service in cmark-gfm

2023-03-3122:01:16

CWE-400

CWE-407

GitHub_M

www.cve.org

cve; cmark-gfm; denial of service; polynomial time complexity; resource exhaustion; upgrade; trusted sources; github flavored markdown; vulnerability; time complexity; patch; credit; report; reference; question.

5.3 Medium

CVSS3

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

LOW

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

0.001 Low

EPSS

Percentile

35.0%

JSON

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

CNA Affected

[
  {
    "vendor": "github",
    "product": "cmark-gfm",
    "versions": [
      {
        "version": "< 0.29.0.gfm.10",
        "status": "affected"
      }
    ]
  }
]