CVE-2025-3522

Thunderbird processes the X-Mozilla-External-Attachment-URL header to handle attachments which can be hosted externally. When an email is opened, Thunderbird accesses the specified URL to  determine file size, and navigates to it when the user clicks the attachment. Because the URL is not validated or sanitized, it can reference internal resources like chrome:// or SMB share file:// links, potentially leading to hashed Windows credential leakage and opening the door to more serious security issues. This vulnerability affects Thunderbird < 137.0.2 and Thunderbird < 128.9.2.
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ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
NISTNIST
6.3 MEDIUM
NETWORK
LOW
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L
mozillaCNA
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CISA-ADPADP
6.3 MEDIUM
NETWORK
LOW
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L
Awaiting analysis
This vulnerability is currently awaiting analysis.
Base Score
CVSS 3.x
EPSS Score
Percentile: 16%
Debian logo
Debian Releases
Debian Product
Codename
thunderbird
bullseye
vulnerable
bullseye (security)
1:128.11.0esr-1~deb11u1
fixed
bookworm
1:128.10.0esr-1~deb12u1
fixed
bookworm (security)
1:128.10.1esr-1~deb12u1
fixed
trixie
1:128.10.0esr-1
fixed
sid
1:128.11.0esr-1
fixed
Ubuntu logo
Ubuntu Releases
Ubuntu Product
Codename
thunderbird
plucky
not-affected
oracular
not-affected
noble
not-affected
jammy
needs-triage
focal
needs-triage