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Vulnerabilities

Vulnerability · 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.

Published Apr 15, 2025 · catalog updated Apr 13, 2026 · When an email contains

Check if you run it

No confirmed exploitation is on record for CVE-2025-3523. EPSS is 0.32%. Act only if a listed version of When an email contains is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (When an email contains).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium6.4
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.32%
Remediation
Advisory link
Affected products
vendor mozilla

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • vendor mozillaversion unspecified

How to fix CVE-2025-3523

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2025-3523. EPSS is 0.32%. Act only if a listed version of When an email contains is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.32%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Apr 15, 2025 · EUVD

    Detected

    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.

  2. Apr 13, 2026 · EUVD

    Updated

    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.

Sources

  • CVE.orgVulnerability recordCVE-2025-3523

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2025-3523

    30-day exploitation probability 0.3%

    first.org
  • EUVDVulnerability recordEUVD-2025-10966

    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 downloadin

    euvd.enisa.europa.eu

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.