Service interruption via filename regex backtracking
Published May 12, 2026 · Updated May 12, 2026
ReDoS in PillarJS multiparty 4.2.3 and earlier allows remote attackers to block the Node.js event loop via a crafted multipart upload. The Content-Disposition filename parser applies an inefficient backtracking regular expression to attacker-controlled header text, and an approximately 8 KB repeated filename fragment consumes seconds of CPU time. Any network service that passes multipart uploads to the library is exposed without authentication, stalling request processing on its event loop.
Summary
What happened
ReDoS in PillarJS multiparty 4.2.3 and earlier allows remote attackers to block the Node.js event loop via a crafted multipart upload. The Content-Disposition filename parser applies an inefficient backtracking regular expression to attacker-controlled header text, and an approximately 8 KB repeated filename fragment consumes seconds of CPU time. Any network service that passes multipart uploads to the library is exposed without authentication, stalling request processing on its event loop.
The record
- CVE
- CVE-2026-8159
- Published
- May 12, 2026
- Updated
- May 12, 2026
- Vendor
- PillarJS
- Product
- multiparty
- Classifications
- CWE-1333, T1499
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 12, 2026CVE publishedPublication date reported by the CVE source.
- May 12, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=0 <=4.2.3
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What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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