{"id":"UBUNTU-CVE-2025-3909","details":"Thunderbird's handling of the X-Mozilla-External-Attachment-URL header can be exploited to execute JavaScript in the file:/// context. By crafting a nested email attachment (message/rfc822) and setting its content type to application/pdf, Thunderbird may incorrectly render it as HTML when opened, allowing the embedded JavaScript to run without requiring a file download. This behavior relies on Thunderbird auto-saving the attachment to /tmp and linking to it via the file:/// protocol, potentially enabling JavaScript execution as part of the HTML. This vulnerability was fixed in Thunderbird 128.10.1 and Thunderbird 138.0.1.","modified":"2026-05-14T14:15:56.618787Z","published":"2025-05-14T17:15:00Z","related":["USN-7663-1"],"upstream":["CVE-2025-3909"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2025-3909"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2025-3909"},{"type":"REPORT","url":"https://www.mozilla.org/en-US/security/advisories/mfsa2025-34/#CVE-2025-3909"},{"type":"REPORT","url":"https://bugzilla.mozilla.org/show_bug.cgi?id=1958376"},{"type":"REPORT","url":"https://www.mozilla.org/security/advisories/mfsa2025-34/"},{"type":"REPORT","url":"https://www.mozilla.org/security/advisories/mfsa2025-35/"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-7663-1"}],"affected":[{"package":{"name":"thunderbird","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/thunderbird@1:128.12.0+build1-0ubuntu0.22.04.1?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1:128.12.0+build1-0ubuntu0.22.04.1"}]}],"versions":["1:91.1.2+build1-0ubuntu1","1:91.3.0+build2-0ubuntu1","1:91.3.1+build1-0ubuntu1","1:91.3.2+build1-0ubuntu1","1:91.4.0+build1.1-0ubuntu1","1:91.4.0+build2-0ubuntu1","1:91.5.0+build1-0ubuntu1","1:91.5.1+build1-0ubuntu1","1:91.6.1+build1-0ubuntu1","1:91.7.0+build1-0ubuntu1","1:91.7.0+build2-0ubuntu1","1:91.8.0+build2-0ubuntu1","1:91.9.1+build1-0ubuntu0.22.04.1","1:91.11.0+build2-0ubuntu0.22.04.1","1:102.2.2+build1-0ubuntu0.22.04.1","1:102.4.2+build2-0ubuntu0.22.04.1","1:102.7.1+build2-0ubuntu0.22.04.1","1:102.8.0+build2-0ubuntu0.22.04.1","1:102.9.0+build1-0ubuntu0.22.04.1","1:102.10.0+build2-0ubuntu0.22.04.1","1:102.11.0+build1-0ubuntu0.22.04.1","1:102.13.0+build1-0ubuntu0.22.04.1","1:102.15.0+build1-0ubuntu0.22.04.1","1:102.15.1+build1-0ubuntu0.22.04.1","1:115.3.1+build1-0ubuntu0.22.04.2","1:115.4.1+build1-0ubuntu0.22.04.1","1:115.5.0+build1-0ubuntu0.22.04.1","1:115.6.0+build2-0ubuntu0.22.04.1","1:115.8.1+build1-0ubuntu0.22.04.1","1:115.9.0+build1-0ubuntu0.22.04.1","1:115.10.1+build1-0ubuntu0.22.04.1","1:115.11.0+build2-0ubuntu0.22.04.1","1:115.12.0+build3-0ubuntu0.22.04.1","1:115.13.0+build5-0ubuntu0.22.04.1","1:115.15.0+build1-0ubuntu0.22.04.1","1:115.16.0+build2-0ubuntu0.22.04.1","1:115.18.0+build1-0ubuntu0.22.04.1"],"ecosystem_specific":{"binaries":[{"binary_version":"1:128.12.0+build1-0ubuntu0.22.04.1","binary_name":"thunderbird"},{"binary_version":"1:128.12.0+build1-0ubuntu0.22.04.1","binary_name":"thunderbird-gnome-support"},{"binary_version":"1:128.12.0+build1-0ubuntu0.22.04.1","binary_name":"thunderbird-mozsymbols"},{"binary_version":"1:128.12.0+build1-0ubuntu0.22.04.1","binary_name":"xul-ext-calendar-timezones"},{"binary_version":"1:128.12.0+build1-0ubuntu0.22.04.1","binary_name":"xul-ext-gdata-provider"},{"binary_version":"1:128.12.0+build1-0ubuntu0.22.04.1","binary_name":"xul-ext-lightning"}],"availability":"No subscription required"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2025/UBUNTU-CVE-2025-3909.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N"},{"type":"Ubuntu","score":"medium"}]}