Service hang via overlapping lexer regexes
Published Mar 17, 2021 · Updated Aug 3, 2024
Regular expression denial of service in Pygments 1.1 through 2.7.3 allows attackers to hang syntax highlighting with crafted source text. Multiple language lexers apply overlapping quantified groups and wildcard subpatterns to repeated digits, spaces, or delimiters, causing exponential or cubic backtracking. A reachable application must pass attacker-controlled text to an affected lexer; the resulting CPU exhaustion stalls highlighting and can interrupt the hosting service.
Summary
What happened
Regular expression denial of service in Pygments 1.1 through 2.7.3 allows attackers to hang syntax highlighting with crafted source text. Multiple language lexers apply overlapping quantified groups and wildcard subpatterns to repeated digits, spaces, or delimiters, causing exponential or cubic backtracking. A reachable application must pass attacker-controlled text to an affected lexer; the resulting CPU exhaustion stalls highlighting and can interrupt the hosting service.
The record
- CVE
- CVE-2021-27291
- Published
- Mar 17, 2021
- Updated
- Aug 3, 2024
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-1333, T1499
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 17, 2021CVE publishedPublication date reported by the CVE source.
- Aug 3, 2024Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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What is affected?
Affected products and versions are unavailable in this record.
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
- Doyensec Pygments ReDoS reproduction recipesproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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