CVE-2026-4926 — path-to-regexp vulnerable to Denial of Service via sequential optional groups
Impact: A bad regular expression is generated any time you have multiple sequential optional groups (curly brace syntax), such as `{a}{b}{c}:z`. The generated regex grows expon…
Published: 2026-03-26 · CVSS: 7.5 · CVSS 3.1
Impact: A bad regular expression is generated any time you have multiple sequential optional groups (curly brace syntax), such as `{a}{b}{c}:z`. The generated regex grows exponentially with the number of groups, causing denial of service. Patches: Fixed in version 8.4.0. Workarounds: Limit the number of sequential optional groups in route patterns. Avoid passing user-controlled input as route patterns.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7