Denial of service via regex backtracking
Published Sep 17, 2021 · Updated Aug 3, 2024
Regular expression denial of service in nth-check before 2.0.1 allows attackers to hang a consuming process via a crafted invalid formula. The parse function applies an anchored regex whose optional whitespace and numeric groups overlap, causing excessive backtracking on long invalid nth-child expressions. A consuming application must pass attacker-controlled formula text to parse; exploitation monopolizes its JavaScript process without data exposure or modification.
Summary
What happened
Regular expression denial of service in nth-check before 2.0.1 allows attackers to hang a consuming process via a crafted invalid formula. The parse function applies an anchored regex whose optional whitespace and numeric groups overlap, causing excessive backtracking on long invalid nth-child expressions. A consuming application must pass attacker-controlled formula text to parse; exploitation monopolizes its JavaScript process without data exposure or modification.
The record
- CVE
- CVE-2021-3803
- Published
- Sep 17, 2021
- Updated
- Aug 3, 2024
- Vendor
- Felix Boehm
- Product
- nth-check
- Classifications
- CWE-1333, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 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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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=unspecified <2.0.1
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.
Weakness, pattern, technique
Public exploit references
- GitHub Advisory ReDoS proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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