Vulnerability in Mozilla Thunderbird
CVE-2025-3523
When an email contains multiple attachments with external links via the X-Mozilla-External-Attachment-URL header, only the last link is shown when hovering over any attachment. Although the correct link is used on click, the misleading hover text could trick users into downloading content from untrusted sources. This vulnerability was fixed in Thunderbird 137.0.2 and Thunderbird 128.9.2.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.4 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:H/A:L.
EPSS exploit prediction
EPSS: 0.003 (21.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 22nd percentile — 21.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: +0.000
Affected products
- Mozilla Thunderbird — versions 128.9.2, 137.0.2
Weakness classification (CWE)
Public proof-of-concept exploits
References
- bugzilla.mozilla.org/show_bug.cgi (Permissions Required)
- www.mozilla.org/security/advisories/mfsa2025-26/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-27/ (Vendor Advisory)
Frequently asked questions
- What is CVE-2025-3523?
- CVE-2025-3523 is a medium-severity vulnerability in Mozilla Thunderbird, classified under User Interface (UI) Misrepresentation of Critical Information. CVSS score: 6.4/10. Published 2025-04-15.
- How severe is CVE-2025-3523?
- Medium severity. CVSS v3 base score is 6.4 out of 10.
- Is CVE-2025-3523 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.