PatchTheCVECVE-2026-8159: multiparty@4.2.3 and lower versions are vulnerable to denial of service via regular expression backtracking in
CVE-2026-8159 is a high-severity flaw (CVSS 7.5) affecting multiparty. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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 elimina
Why this priority
- High severity
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 7.5 (High) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 0.3% (top 73%) |
| CISA exploited list | No |
| Weakness | CWE-1333 |
| Published | 2026-05-12 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-8159?
multiparty: upgrade to 4.3.0. Exact commands for each OS are on this page.
Is CVE-2026-8159 being exploited?
CVE-2026-8159 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-8159 affect?
CVE-2026-8159 affects multiparty. Severity is high (CVSS 7.5). 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 t
How urgent is CVE-2026-8159?
Priority 38/100. High severity; Remotely exploitable, no login, no user action
Related CVEs
- CVE-2026-8162 HIGH 7.5 UPGRADE multiparty@4.2.3 and lower versions are vulnerable to denial of service via uncaught exception
- CVE-2026-8161 HIGH 7.5 UPGRADE multiparty@4.2.3 and lower versions are vulnerable to denial of service via uncaught exception