How severe is CVE-2026-3889?

CVE-2026-3889 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2026-3889 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (10th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-3889?

CVE-2026-3889 primarily affects Mozilla Thunderbird. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-3889?

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

Does CVE-2026-3889 have an EU (EUVD) identifier?

Yes. CVE-2026-3889 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-15019.

When was CVE-2026-3889 published?

CVE-2026-3889 was published on 2026-03-24 and last updated on 2026-06-17.

CVE-2026-3889

CVE-2026-3889 is a medium-severity vulnerability in Mozilla Thunderbird with a CVSS 3.x base score of 6.5. 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 6.5)
EPSS exploit prediction: 0% (10th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-15019
Weakness: CWE-451
Affected product: Mozilla Thunderbird
Published: 2026-03-24
Last modified: 2026-06-17

Description

Spoofing issue in Thunderbird. This vulnerability was fixed in Thunderbird 149 and Thunderbird 140.9.

Frequently asked questions

What is CVE-2026-3889?: Spoofing issue in Thunderbird. This vulnerability was fixed in Thunderbird 149 and Thunderbird 140.9.
How severe is CVE-2026-3889?: CVE-2026-3889 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2026-3889 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (10th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-3889?: CVE-2026-3889 primarily affects Mozilla Thunderbird. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-3889?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-3889 have an EU (EUVD) identifier?: Yes. CVE-2026-3889 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-15019.
When was CVE-2026-3889 published?: CVE-2026-3889 was published on 2026-03-24 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*

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