What is CVE-2026-4923?

CVE-2026-4923 is a medium-severity vulnerability in Path-to-regexp, classified under Inefficient Regular Expression Complexity. CVSS score: 5.9/10. Published 2026-03-26.

How severe is CVE-2026-4923?

Medium severity. CVSS v3 base score is 5.9 out of 10.

Vulnerability in Path-to-regexp

CVE-2026-4923

Impact: When using multiple wildcards, combined with at least one parameter, a regular expression can be generated that is vulnerable to ReDoS. This backtracking vulnerability requires the second wildcard to be somewhere other than the en…

Vulnerability class: ReDoS (Regular Expression Denial of Service)

EPSS: 0.000 (5.1th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.

Affected products

Path-to-regexp — versions 8.0.0, 8.4.0

Weakness classification (CWE)

CWE-1333 — Inefficient Regular Expression Complexity

References

cna.openjsf.org/security-advisories.html

Frequently asked questions

What is CVE-2026-4923?: CVE-2026-4923 is a medium-severity vulnerability in Path-to-regexp, classified under Inefficient Regular Expression Complexity. CVSS score: 5.9/10. Published 2026-03-26.
How severe is CVE-2026-4923?: Medium severity. CVSS v3 base score is 5.9 out of 10.