Service interruption via inefficient parse regex
Published Jan 5, 2023 · Updated Nov 3, 2025
Regular expression denial of service in Vercel ms before 2.0.0 allows remote attackers to delay Node.js event-loop processing via crafted input. The index.js parse function converts its argument to a string, permits up to 10,000 characters, and runs an inefficient anchored numeric-unit regular expression against the entire value. Exposure requires a consuming application to pass attacker-controlled strings to ms(); one near-limit nonmatching string was demonstrated to occupy the event loop for about 0.3 seconds.
Summary
What happened
Regular expression denial of service in Vercel ms before 2.0.0 allows remote attackers to delay Node.js event-loop processing via crafted input. The index.js parse function converts its argument to a string, permits up to 10,000 characters, and runs an inefficient anchored numeric-unit regular expression against the entire value. Exposure requires a consuming application to pass attacker-controlled strings to ms(); one near-limit nonmatching string was demonstrated to occupy the event loop for about 0.3 seconds.
The record
- CVE
- CVE-2017-20162
- Published
- Jan 5, 2023
- Updated
- Nov 3, 2025
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-1333, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jan 5, 2023CVE publishedPublication date reported by the CVE source.
- Nov 3, 2025Record updatedLatest update available in the CVE record.
Exploitability
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What is affected?
Affected products and versions are unavailable in this record.
Published CVSS scores
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Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
- ms parse ReDoS proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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