CVE-2023-22485: cmark-gfm out-of-bounds read in validate_protocol

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2023-01-24 · updated 2026-06-17
Weakness: CWE-125

Description

cmark-gfm is GitHub's fork of cmark, a CommonMark parsing and rendering library and program in C. In versions prior 0.29.0.gfm.7, a crafted markdown document can trigger an out-of-bounds read in the `validate_protocol` function. We believe this bug is harmless in practice, because the out-of-bounds read accesses `malloc` metadata without causing any visible damage.This vulnerability has been patched in 0.29.0.gfm.7.

Affected products

github cmark-gfm: before 0.29.0.gfm.7 — fixed in 0.29.0.gfm.7

How to fix

Upgrade to a fixed version: github cmark-gfm 0.29.0.gfm.7. Check the vendor advisory for mitigations.

References

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