Allowed UNC hostnames for attachments interpreted as a regular expression
Summary
| CVE | CVE-2026-84642 |
|---|---|
| State | PUBLISHED |
| Assigner | mozilla |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-09-01 22:17:20 UTC |
| Updated | 2026-09-01 22:17:20 UTC |
| Description | 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. |
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Mozilla | Thunderbird | unaffected 153.2 153.* rpm | Not specified |
| CNA | Mozilla | Thunderbird | unaffected 155 * rpm | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| bugzilla.mozilla.org/show_bug.cgi | [email protected] | bugzilla.mozilla.org | |
| www.mozilla.org/security/advisories/mfsa2026-88 | [email protected] | www.mozilla.org | |
| www.mozilla.org/security/advisories/mfsa2026-86 | [email protected] | www.mozilla.org | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: ChinhNguyen, Lowk3yz (en)
There are currently no legacy QID mappings associated with this CVE.