What is CVE-2026-4867?

CVE-2026-4867 is a high-severity vulnerability in Path-to-regexp, classified under Inefficient Regular Expression Complexity. CVSS score: 7.5/10. Published 2026-03-26.

How severe is CVE-2026-4867?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Path-to-regexp

CVE-2026-4867

Impact: A bad regular expression is generated any time you have three or more parameters within a single segment, separated by something that is not a period (.). For example, /:a-:b-:c or /:a-:b-:c-:d. The backtrack protection added in p…

Vulnerability class: ReDoS (Regular Expression Denial of Service)

EPSS: 0.000 (5.0th percentile) — read the EPSS interpretation.

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.

Affected products

Path-to-regexp — versions 0

Weakness classification (CWE)

CWE-1333 — Inefficient Regular Expression Complexity

References

github.com/advisories/GHSA-9wv6-86v2-598j
blakeembrey.com/posts/2024-09-web-redos
cna.openjsf.org/security-advisories.html

Frequently asked questions

What is CVE-2026-4867?: CVE-2026-4867 is a high-severity vulnerability in Path-to-regexp, classified under Inefficient Regular Expression Complexity. CVSS score: 7.5/10. Published 2026-03-26.
How severe is CVE-2026-4867?: High severity. CVSS v3 base score is 7.5 out of 10.