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{"cveTags": [], "descriptions": [{"lang": "en", "value": "Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10."}], "id": "CVE-2026-6771", "lastModified": "2026-04-22T00:16:33.850", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 9.8, "baseSeverity": "CRITICAL", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 5.9, "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}, "published": "2026-04-21T13:16:22.927", "references": [{"source": "security@mozilla.org", "url": "https://bugzilla.mozilla.org/show_bug.cgi?id=2025067"}, {"source": "security@mozilla.org", "url": "https://www.mozilla.org/security/advisories/mfsa2026-30/"}, {"source": "security@mozilla.org", "url": "https://www.mozilla.org/security/advisories/mfsa2026-32/"}, {"source": "security@mozilla.org", "url": "https://www.mozilla.org/security/advisories/mfsa2026-33/"}, {"source": "security@mozilla.org", "url": "https://www.mozilla.org/security/advisories/mfsa2026-34/"}], "sourceIdentifier": "security@mozilla.org", "vulnStatus": "Undergoing Analysis", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-288"}], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "[140.10,140.*]"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "[150,*]"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "Firefox", "source": "cna", "vendor": "Mozilla"}, "product": "firefox", "vendor": "mozilla"}], "analysis": {"en": {"generated_at": "2026-04-21T22:54:40.463976+00:00", "value": {"mitigation_remediation": ["Update Mozilla Firefox to version 150 or newer, or to ESR 140.10 or newer.", "Disable or remove extensions that alter the DOM or modify browser security settings to avoid conflicts with the built\u2011in mitigations.", "If updating is not immediately possible, enforce strict content\u2011security policies and restrict script execution on untrusted pages to reduce the attack surface."], "summary": {"action": "Patch immediately", "impact": "Bypassing DOM security measures"}, "threat_synthesis": {"affected_systems": "Mozilla Firefox before version 150 and the ESR 140.10 branch are affected. Users of any earlier release are susceptible until they upgrade to the patched versions.", "description_and_impact": "The vulnerability, named \"Mitigation bypass in the DOM: Security component,\" allows an attacker to circumvent the security protections implemented within Firefox\u2019s Document Object Model environment. This defect can enable malicious scripts to execute with elevated privileges or alter web content without the browser\u2019s safeguards, potentially compromising the confidentiality, integrity, or availability of user data. The weakness aligns with known security control misconfiguration issues.", "risk_and_exploitability": "Risk appears high due to the potential to bypass critical web security measures, yet EPSS data is unavailable and the vulnerability is not in the CISA KEV list, suggesting limited known exploitation. The attack vector is likely client\u2011side, where a malicious web page or local content can exploit the omission of the DOM security component. Without an official workaround, the only reliable defense is to upgrade Firefox to the fixed version."}}}}, "created": "2026-04-21T16:45:15.073962+00:00", "updated": "2026-04-21T23:00:03.492481+00:00", "vendors": ["mozilla", "mozilla$PRODUCT$firefox"], "weaknesses": ["CWE-693", "CWE-200"]}