What’s Vulnerable › Vulnerabilities

CVE-2026-8159: multiparty vulnerable to ReDoS via filename parsing

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-05-12 · updated 2026-06-17
• Weakness: CWE-1333

Description

multiparty@4.2.3 and lower versions are vulnerable to denial of service via regular expression backtracking in the Content-Disposition filename parameter parser. A crafted multipart upload with a long header value can cause regex matching to take seconds, blocking the event loop. Impact: any service accepting multipart uploads via multiparty is affected. Workarounds: limiting upload sizes at the proxy or gateway layer reduces but does not eliminate the attack surface, since a small header of around 8 KB is sufficient to trigger the vulnerable backtracking. Upgrade to multiparty@4.3.0 or higher.

Affected products

• multiparty: before 4.3.0 — fixed in 4.3.0

How to fix

Upgrade to a fixed version: multiparty 4.3.0. Check the vendor advisory for mitigations.

References

• https://cna.openjsf.org/security-advisories.html
• https://github.com/pillarjs/multiparty/security/advisories/GHSA-65x3-rw7q-gx94
• https://owasp.org/www-community/attacks/Regular_expression_Denial_of_Service_-_ReDoS

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