What is CVE-2025-3932?

CVE-2025-3932 is a medium-severity vulnerability in Mozilla Thunderbird, classified under Authentication Bypass Using an Alternate Path or Channel. CVSS score: 6.5/10. Published 2025-05-14.

How severe is CVE-2025-3932?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Is CVE-2025-3932 known to be exploited?

2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Vulnerability in Mozilla Thunderbird

CVE-2025-3932

It was possible to craft an email that showed a tracking link as an attachment. If the user attempted to open the attachment, Thunderbird automatically accessed the link. The configuration to block remote content did not prevent that. Thunderbird has been fixed to no longer allow access to web pages listed in the X-Mozilla-External-Attachment-URL header of an email. This vulnerability was fixed in Thunderbird 128.10.1 and Thunderbird 138.0.1.

EPSS: 0.003 (25.1th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N.

Affected products

Mozilla Thunderbird — versions 128.10.1, 138.0.1

Weakness classification (CWE)

CWE-288 — Authentication Bypass Using an Alternate Path or Channel

Public proof-of-concept exploits

References

security@mozilla.org (Permissions Required)
security@mozilla.org (Vendor Advisory)
security@mozilla.org (Vendor Advisory)
af854a3a-2127-422b-91ae-364da2661108

Frequently asked questions

What is CVE-2025-3932?: CVE-2025-3932 is a medium-severity vulnerability in Mozilla Thunderbird, classified under Authentication Bypass Using an Alternate Path or Channel. CVSS score: 6.5/10. Published 2025-05-14.
How severe is CVE-2025-3932?: Medium severity. CVSS v3 base score is 6.5 out of 10.
Is CVE-2025-3932 known to be exploited?: 2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.