Inefficient regular expression complexity in path-to-regexp - CVE-2026-4867
Published: April 22, 2026
Vulnerability identifier: #VU126856
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-4867
CWE-ID: CWE-1333
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: pillarjs
Affected software:
path-to-regexp
path-to-regexp
Detailed vulnerability description
The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.
The vulnerability exists due to 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 (.). A remote attacker can pass specially crafted data to the application and perform regular expression denial of service (ReDos) attack.
How to mitigate CVE-2026-4867
Install updates from vendor's website.