CVE-2026-84642
highThe values of the mail.allowed_attachment_hostnames advanced config setting were used in a regular expression without escaping.
Vendor / product: Mozilla — thunderbird
The values of the mail.allowed_attachment_hostnames advanced config setting were used in a regular expression without escaping. For some possible valid hostnames, this could allow certain unintended hostnames to also match and serve remote attachments. This vulnerability was fixed in Thunderbird 155 and Thunderbird 153.2.
CVSS
7.5
7.5 (CVSS v3.1)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N Severity source: NVD CVSS v3.1 (134c704f-9b21-4f2e-91b3-4a467353bcc0)
Timeline (UTC)
Published: 2026-09-01 22:17
Modified: 2026-09-03 19:00
NVD status: Analyzed
Last synced 2 days ago
Verified against the source API 2026-10-27 06:50 UTC
Exploitation
Not listed in CISA KEV (as of last catalog sync)
Absence from KEV does not mean a CVE is not exploited. Exploitation status: unknown (no authoritative evidence in our sources).
Affected products
mozilla / thunderbird <153.2.0, ≥154.0 <155.0
Weakness classification (CWE)
Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.
Mitigation & advisories
Vendor advisory: https://www.mozilla.org/security/advisories/mfsa2026-86/
Vendor advisory: https://www.mozilla.org/security/advisories/mfsa2026-88/
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=2060462 security@mozilla.org
- https://www.mozilla.org/security/advisories/mfsa2026-86/ security@mozilla.org
- https://www.mozilla.org/security/advisories/mfsa2026-88/ security@mozilla.org
Data sources
NVD CVE API 2.0 — fetched 2026-10-27 06:50 UTC · record ↗