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Vulnerabilities

Vulnerability · 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.

Published May 12, 2026 · catalog updated Jun 17, 2026 · multiparty@4.2.3 and lower versions

Check if you run it

No confirmed exploitation is on record for CVE-2026-8159. EPSS is 0.62%. Act only if a listed version of multiparty@4.2.3 and lower versions is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (multiparty@4.2.3 and lower versions).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High7.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.62%
Remediation
Advisory link
Affected products
cpe pillarjs/multiparty

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe pillarjs/multipartyversion unspecified

How to fix CVE-2026-8159

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-8159. EPSS is 0.62%. Act only if a listed version of multiparty@4.2.3 and lower versions is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-1333: Inefficient Regular Expression Complexity. EPSS 0.62%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. May 12, 2026 · NIST NVD

    Detected

    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 p

  2. Jun 17, 2026 · NIST NVD

    Updated

    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 p

Sources

  • CVE.orgVulnerability recordCVE-2026-8159

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-8159

    30-day exploitation probability 0.6%

    first.org
  • NIST NVDVulnerability recordCVE-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.

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.