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{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,6.2.1)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "fast-jwt", "source": "cna", "vendor": "nearform"}, "product": "fast-jwt", "vendor": "nearform"}], "analysis": {"en": {"generated_at": "2026-04-09T16:22:31.002196+00:00", "value": {"mitigation_remediation": ["Upgrade fast-jwt to version 6.2.1 or later."], "summary": {"action": "Patch", "impact": "Authentication Failure / Denial"}, "threat_synthesis": {"affected_systems": "The issue is present in the nearform fast\u2011jwt library, affecting all releases prior to version 6.2.1. The defect was addressed in the 6.2.1 release and later. Applications that depend on fast\u2011jwt for JWT validation and that use RegExp modifiers /g or /y in the claim\u2011validation options are impacted.", "description_and_impact": "A stateful RegExp modifier applied to claims such as allowedAud, allowedIss, allowedSub, allowedJti, or allowedNonce causes every second verification attempt to fail, even when the token is valid. The effect is a logical denial\u2011of\u2011service in authentication, where 50% of legitimate requests are rejected with no unauthorized access or data breach.", "risk_and_exploitability": "The CVSS score of 5.3 reflects moderate impact. No EPSS score is available and the vulnerability is not listed in the CISA KEV catalog. An attacker who can influence the verification call (for example by controlling the RegExp flags in the payload or by submitting crafted tokens to an authentication endpoint) would cause intermittent authentication failures, potentially degrading service availability. Direct exploitation does not lead to privilege escalation or data disclosure."}}}}, "created": "2026-04-10T08:53:19.727746+00:00", "updated": "2026-04-10T09:32:32.470253+00:00", "vendors": ["nearform", "nearform$PRODUCT$fast-jwt"]}