How severe is CVE-2025-3523?

CVE-2025-3523 has a CVSS 3.x base score of 6.4, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity high, and availability low.

Is CVE-2025-3523 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (20th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-3523?

CVE-2025-3523 affects Mozilla Thunderbird. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2025-3523?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2025-3523 have an EU (EUVD) identifier?

Yes. CVE-2025-3523 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-10966.

When was CVE-2025-3523 published?

CVE-2025-3523 was published on 2025-04-15 and last updated on 2026-06-17.

CVE-2025-3523

CVE-2025-3523 is a medium-severity vulnerability in Mozilla Thunderbird with a CVSS 3.x base score of 6.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-451.

Key facts

Severity: Medium (CVSS 3.x base score 6.4)
EPSS exploit prediction: 0% (20th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-10966
Weakness: CWE-451
Affected product: Mozilla Thunderbird
Published: 2025-04-15
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is 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.
How severe is CVE-2025-3523?: CVE-2025-3523 has a CVSS 3.x base score of 6.4, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity high, and availability low.
Is CVE-2025-3523 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (20th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-3523?: CVE-2025-3523 affects Mozilla Thunderbird. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2025-3523?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-3523 have an EU (EUVD) identifier?: Yes. CVE-2025-3523 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-10966.
When was CVE-2025-3523 published?: CVE-2025-3523 was published on 2025-04-15 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*

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