{"cve":"CVE-2026-4926","nvd":{"published":"2026-03-26T19:17:08.387","modified":"2026-09-09T13:20:25.320","status":"Modified","description":"Impact:\n\nA 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.\n\nPatches:\n\nFixed in version 8.4.0.\n\nWorkarounds:\n\nLimit the number of sequential optional groups in route patterns. Avoid passing user-controlled input as route patterns.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5},"cwes":["CWE-400","CWE-1333"],"references":["https://cna.openjsf.org/security-advisories.html","https://access.redhat.com/errata/RHSA-2026:10153","https://access.redhat.com/errata/RHSA-2026:10172","https://access.redhat.com/errata/RHSA-2026:10175","https://access.redhat.com/errata/RHSA-2026:13545"],"products":["pillarjs:path-to-regexp"],"source":"nvd","synced_at":"2026-10-19T22:28:18.033120106+00:00"},"epss":{"cve":"CVE-2026-4926","score":0.00805,"percentile":0.56782,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-j3q9-mxjg-w52f","url":"https://osv.dev/vulnerability/GHSA-j3q9-mxjg-w52f","summary":"path-to-regexp vulnerable to Denial of Service via sequential optional groups","modified":"2026-09-10T03:50:39.762014882Z","packages":[{"ecosystem":"npm","name":"path-to-regexp","purl":"pkg:npm/path-to-regexp","ranges":[">=8.0.0 <8.4.0"],"fixed":["8.4.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}