Malloc-metadata under-read via unchecked protocol lookbehind
Published Jan 24, 2023 · Updated Mar 10, 2025
Buffer under-read in GitHub cmark-gfm before 0.29.0.gfm.7 allows attackers to trigger a malloc-metadata read via crafted Markdown. The validate_protocol function indexes backward from the current autolink pointer without proving that the protocol and preceding character remain inside the input buffer. The autolink extension must process crafted address-like text, and GitHub reports no visible practical damage beyond the instrumented memory-error report.
Summary
What happened
Buffer under-read in GitHub cmark-gfm before 0.29.0.gfm.7 allows attackers to trigger a malloc-metadata read via crafted Markdown. The validate_protocol function indexes backward from the current autolink pointer without proving that the protocol and preceding character remain inside the input buffer. The autolink extension must process crafted address-like text, and GitHub reports no visible practical damage beyond the instrumented memory-error report.
The record
- CVE
- CVE-2023-22485
- Published
- Jan 24, 2023
- Updated
- Mar 10, 2025
- Vendor
- Product
- cmark-gfm
- Classifications
- CWE-125, CWE-127
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jan 24, 2023CVE publishedPublication date reported by the CVE source.
- Mar 10, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 0.29.0.gfm.7
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
- GitHub autolink under-read proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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