{"id":"CVE-2026-100809","title":"Same-origin policy bypass in the DevTools component","summary":"Same-origin policy bypass in the DevTools component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 153.4, and Firefox 157.","severity":"high","cvss":8.1,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N","cwe":["CWE-346"],"vendor":"mozilla","product":"firefox","affected":["firefox < 153.4.0","firefox >= 154.0.0, < 157.0.0","thunderbird < 153.4.0","thunderbird >= 154.0, < 157.0"],"patched":["firefox 157.0.0","thunderbird 157.0"],"published":"2026-09-29","updated":"2026-10-05","sourceUpdated":"2026-10-05T14:30:57.960","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-100809","references":[{"url":"https://bugzilla.mozilla.org/show_bug.cgi?id=2063658","label":"security@mozilla.org"},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-100/","label":"security@mozilla.org"},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-101/","label":"security@mozilla.org"},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-103/","label":"security@mozilla.org"},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-97/","label":"security@mozilla.org"}],"tags":["nvd","cve.org"],"epss":0.00153,"epssPercentile":0.04351,"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-01T15:30:21.266547Z"},"ingestedAt":"2026-09-29T13:34:31.672Z","slug":"CVE-2026-100809","body":"## Overview\n\nSame-origin policy bypass in the DevTools component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 153.4, and Firefox 157.\n\n## Affected\n\n- `firefox < 153.4.0`\n- `firefox >= 154.0.0, < 157.0.0`\n- `thunderbird < 153.4.0`\n- `thunderbird >= 154.0, < 157.0`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `firefox 157.0.0`\n- `thunderbird 157.0`","depth":"twilight","depthScore":45,"depthScoreParts":{"impact":44.6,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":214363,"id":"CVE-2026-100809","ts":1790869801115,"field":"cvss","old":null,"new":"8.1"},{"seq":214362,"id":"CVE-2026-100809","ts":1790869801115,"field":"severity","old":"none","new":"high"}]}