Denial of service via quadratic Markdown rendering
Published Mar 31, 2023 · Updated Feb 11, 2025
Quadratic rendering in GitHub cmark-gfm before 0.29.0.gfm.10 allows attackers to exhaust CPU with crafted Markdown input. The renderers repeatedly traverse ancestor or prior-sibling chains for individual nodes instead of retaining traversal state, causing nested emphasis and list structures to require quadratic work. An application must render attacker-controlled Markdown through an affected output path; the resulting resource exhaustion can interrupt that application.
Summary
What happened
Quadratic rendering in GitHub cmark-gfm before 0.29.0.gfm.10 allows attackers to exhaust CPU with crafted Markdown input. The renderers repeatedly traverse ancestor or prior-sibling chains for individual nodes instead of retaining traversal state, causing nested emphasis and list structures to require quadratic work. An application must render attacker-controlled Markdown through an affected output path; the resulting resource exhaustion can interrupt that application.
The record
- CVE
- CVE-2023-26485
- Published
- Mar 31, 2023
- Updated
- Feb 11, 2025
- Vendor
- Product
- cmark-gfm
- Classifications
- CWE-407, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 31, 2023CVE publishedPublication date reported by the CVE source.
- Feb 11, 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.10
What conditions does exploitation require?
What is affected?
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.
Weakness, pattern, technique
Public exploit references
- GitHub advisory quadratic-rendering 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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