High severity8.1NVD Advisory· Published May 14, 2025· Updated Apr 13, 2026
CVE-2025-3909
CVE-2025-3909
Description
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.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
Affected products
9cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*+ 1 more
- cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*range: <128.10.1
- (no CPE)range: <128.10.1, <138.0.1
- osv-coords7 versionspkg:rpm/almalinux/thunderbirdpkg:rpm/opensuse/MozillaThunderbird&distro=openSUSE%20Leap%2015.6pkg:rpm/opensuse/MozillaThunderbird&distro=openSUSE%20Tumbleweedpkg:rpm/suse/MozillaThunderbird&distro=SUSE%20Linux%20Enterprise%20Module%20for%20Package%20Hub%2015%20SP6pkg:rpm/suse/MozillaThunderbird&distro=SUSE%20Linux%20Enterprise%20Module%20for%20Package%20Hub%2015%20SP7pkg:rpm/suse/MozillaThunderbird&distro=SUSE%20Linux%20Enterprise%20Workstation%20Extension%2015%20SP6pkg:rpm/suse/MozillaThunderbird&distro=SUSE%20Linux%20Enterprise%20Workstation%20Extension%2015%20SP7
< 128.10.1-1.el10_0.alma.1+ 6 more
- (no CPE)range: < 128.10.1-1.el10_0.alma.1
- (no CPE)range: < 128.10.1-150200.8.215.1
- (no CPE)range: < 128.10.1-1.1
- (no CPE)range: < 128.10.1-150200.8.215.1
- (no CPE)range: < 128.10.1-150200.8.215.1
- (no CPE)range: < 128.10.1-150200.8.215.1
- (no CPE)range: < 128.10.1-150200.8.215.1
Patches
Vulnerability mechanics
References
4- www.mozilla.org/security/advisories/mfsa2025-34/nvdVendor Advisory
- www.mozilla.org/security/advisories/mfsa2025-35/nvdVendor Advisory
- bugzilla.mozilla.org/show_bug.cginvdPermissions Required
- lists.debian.org/debian-lts-announce/2025/05/msg00022.htmlnvd
News mentions
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