CVE-2026-8159: Pillarjs Multiparty

High severity, CVSS 7.5. EPSS: 0.6% chance of exploitation in the next 30 days.

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

• Pillarjs Multiparty: before 4.3.0 (fixed in 4.3.0)

Published 2026-05-12. Last modified 2026-06-17.