CVE-2026-4923

// Vulnerable Route Definition // app.get('/*foo-*bar-:baz', handler) // PoC Request (Conceptual) // Attacker sends a request that triggers catastrophic backtracking // Example: GET /aaaaaaaaaaaaaaaaaaaa-bbbbbbbbbbbbbbbbbbbb-ccccccccccc // This causes the regex engine to backtrack excessively.

{"cve": {"id": "CVE-2026-4923", "sourceIdentifier": "ce714d77-add3-4f53-aff5-83d477b104bb", "published": "2026-03-26T19:17:08.187", "lastModified": "2026-04-16T18:03:37.620", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Impact:\n\nWhen 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 end of the path.\n\nUnsafe examples:\n\n/*foo-*bar-:baz\n/*a-:b-*c-:d\n/x/*a-:b/*c/y\n\nSafe examples:\n\n/*foo-:bar\n/*foo-:bar-*baz\n\nPatches:\n\nUpgrade to version 8.4.0.\n\nWorkarounds:\n\nIf you are using multiple wildcard parameters, you can check the regex output with a tool such as https://makenowjust-labs.github.io/recheck/playground/ to confirm whether a path is vulnerable."}, {"lang": "es", "value": "Impacto:\n\nAl usar múltiples comodines, combinados con al menos un parámetro, se puede generar una expresión regular que es vulnerable a ReDoS. Esta vulnerabilidad de retroceso requiere que el segundo comodín esté en un lugar distinto al final de la ruta.\n\nEjemplos no seguros:\n\n/*foo-*bar-:baz\n/*a-:b-*c-:d\n/x/*a-:b/*c/y\n\nEjemplos seguros:\n\n/*foo-:bar\n/*foo-:bar-*baz\n\nParches:\n\nActualice a la versión 8.4.0.\n\nSoluciones alternativas:\n\nSi está utilizando múltiples parámetros comodín, puede verificar la salida de la expresión regular con una herramienta como https://makenowjust-labs.github.io/recheck/playground/ para confirmar si una ruta es vulnerable."}], "metrics": {"cvssMetricV31": [{"source": "ce714d77-add3-4f53-aff5-83d477b104bb", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 5.9, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.2, "impactScore": 3.6}]}, "weaknesses": [{"source": "ce714d77-add3-4f53-aff5-83d477b104bb", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-1333"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:pillarjs:path-to-regexp:*:*:*:*:*:node.js:*:*", "versionStartIncluding": "8.0.0", "versionEndExcluding": "8.4.0", "matchCriteriaId": "DB421812-F7E3-4CC5-B02B-53CCBFDFB671"}]}]}], "references": [{"url": "https://cna.openjsf.org/security-advisories.html", "source": "ce714d77-add3-4f53-aff5-83d477b104bb", "tags": ["Third Party Advisory"]}]}}