Vulnerability in Multiparty
CVE-2026-8159
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.
Vulnerability class: ReDoS (Regular Expression Denial of Service)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.006 (47.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 47th percentile — 47.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.006 · change: +0.003
Affected products
- Multiparty — versions 0, 4.3.0
- Pillarjs Multiparty
Weakness classification (CWE)
References
- ce714d77-add3-4f53-aff5-83d477b104bb (Mitigation, Vendor Advisory)
- ce714d77-add3-4f53-aff5-83d477b104bb (Not Applicable)
- ce714d77-add3-4f53-aff5-83d477b104bb (Third Party Advisory)
Frequently asked questions
- What is CVE-2026-8159?
- CVE-2026-8159 is a high-severity vulnerability in Multiparty, classified under Inefficient Regular Expression Complexity. CVSS score: 7.5/10. Published 2026-05-12.
- How severe is CVE-2026-8159?
- High severity. CVSS v3 base score is 7.5 out of 10.