CVE-2026-84642
Allowed UNC hostnames for attachments interpreted as a regular expression
CVE-2026-84642 is fixed in 134 products on 3 platforms, first by Mozilla Thunderbird 155.0, released August 28, 2026. It is not reported as exploited. Patch Radar priority: High.
HighFixed on 3 platforms
CVSS
7.5
No vendor severity
Exploitation
None reported
No vendor assessment
CISA KEV
Not listed
Not in the Known Exploited Vulnerabilities catalog
EPSS
0.0042
36th percentile
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.
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Windows apps | |||
| Mozilla Thunderbird (af) | 155.0 | Mozilla Thunderbird (af) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (ar) | 155.0 | Mozilla Thunderbird (ar) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (ast) | 155.0 | Mozilla Thunderbird (ast) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (be) | 155.0 | Mozilla Thunderbird (be) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (bg) | 155.0 | Mozilla Thunderbird (bg) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (br) | 155.0 | Mozilla Thunderbird (br) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (ca) | 155.0 | Mozilla Thunderbird (ca) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (cak) | 155.0 | Mozilla Thunderbird (cak) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (cs) | 155.0 | Mozilla Thunderbird (cs) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (cy) | 155.0 | Mozilla Thunderbird (cy) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (da) | 155.0 | Mozilla Thunderbird (da) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (de) | 155.0 | Mozilla Thunderbird (de) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (dsb) | 155.0 | Mozilla Thunderbird (dsb) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (el) | 155.0 | Mozilla Thunderbird (el) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (en-CA) | 155.0 | Mozilla Thunderbird (en-CA) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (en-GB) | 155.0 | Mozilla Thunderbird (en-GB) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (en-US) | 155.0 | Mozilla Thunderbird (en-US) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (es-AR) | 155.0 | Mozilla Thunderbird (es-AR) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (es-ES) | 155.0 | Mozilla Thunderbird (es-ES) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (es-MX) | 155.0 | Mozilla Thunderbird (es-MX) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (et) | 155.0 | Mozilla Thunderbird (et) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (eu) | 155.0 | Mozilla Thunderbird (eu) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (fi) | 155.0 | Mozilla Thunderbird (fi) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (fr) | 155.0 | Mozilla Thunderbird (fr) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (fy-NL) | 155.0 | Mozilla Thunderbird (fy-NL) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (ga-IE) | 155.0 | Mozilla Thunderbird (ga-IE) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (gd) | 155.0 | Mozilla Thunderbird (gd) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (gl) | 155.0 | Mozilla Thunderbird (gl) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (he) | 155.0 | Mozilla Thunderbird (he) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (hr) | 155.0 | Mozilla Thunderbird (hr) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (hsb) | 155.0 | Mozilla Thunderbird (hsb) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (hu) | 155.0 | Mozilla Thunderbird (hu) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (hy-AM) | 155.0 | Mozilla Thunderbird (hy-AM) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (id) | 155.0 | Mozilla Thunderbird (id) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (is) | 155.0 | Mozilla Thunderbird (is) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (it) | 155.0 | Mozilla Thunderbird (it) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (ja) | 155.0 | Mozilla Thunderbird (ja) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (ka) | 155.0 | Mozilla Thunderbird (ka) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (kab) | 155.0 | Mozilla Thunderbird (kab) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (kk) | 155.0 | Mozilla Thunderbird (kk) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (ko) | 155.0 | Mozilla Thunderbird (ko) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (lt) | 155.0 | Mozilla Thunderbird (lt) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (lv) | 155.0 | Mozilla Thunderbird (lv) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (ms) | 155.0 | Mozilla Thunderbird (ms) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (nb-NO) | 155.0 | Mozilla Thunderbird (nb-NO) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (nl) | 155.0 | Mozilla Thunderbird (nl) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (nn-NO) | 155.0 | Mozilla Thunderbird (nn-NO) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (pa-IN) | 155.0 | Mozilla Thunderbird (pa-IN) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (pl) | 155.0 | Mozilla Thunderbird (pl) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (pt-BR) | 155.0 | Mozilla Thunderbird (pt-BR) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (pt-PT) | 155.0 | Mozilla Thunderbird (pt-PT) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (rm) | 155.0 | Mozilla Thunderbird (rm) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (ro) | 155.0 | Mozilla Thunderbird (ro) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (ru) | 155.0 | Mozilla Thunderbird (ru) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (sk) | 155.0 | Mozilla Thunderbird (sk) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (sl) | 155.0 | Mozilla Thunderbird (sl) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (sq) | 155.0 | Mozilla Thunderbird (sq) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (sr) | 155.0 | Mozilla Thunderbird (sr) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (sv-SE) | 155.0 | Mozilla Thunderbird (sv-SE) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (th) | 155.0 | Mozilla Thunderbird (th) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (tr) | 155.0 | Mozilla Thunderbird (tr) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (uk) | 155.0 | Mozilla Thunderbird (uk) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (uz) | 155.0 | Mozilla Thunderbird (uz) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (vi) | 155.0 | Mozilla Thunderbird (vi) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (zh-CN) | 155.0 | Mozilla Thunderbird (zh-CN) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird (zh-TW) | 155.0 | Mozilla Thunderbird (zh-TW) 155.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (af) | 153.2.0 | Mozilla Thunderbird ESR (af) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (ar) | 153.2.0 | Mozilla Thunderbird ESR (ar) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (ast) | 153.2.0 | Mozilla Thunderbird ESR (ast) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (be) | 153.2.0 | Mozilla Thunderbird ESR (be) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (bg) | 153.2.0 | Mozilla Thunderbird ESR (bg) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (br) | 153.2.0 | Mozilla Thunderbird ESR (br) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (ca) | 153.2.0 | Mozilla Thunderbird ESR (ca) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (cak) | 153.2.0 | Mozilla Thunderbird ESR (cak) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (cs) | 153.2.0 | Mozilla Thunderbird ESR (cs) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (cy) | 153.2.0 | Mozilla Thunderbird ESR (cy) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (da) | 153.2.0 | Mozilla Thunderbird ESR (da) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (de) | 153.2.0 | Mozilla Thunderbird ESR (de) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (dsb) | 153.2.0 | Mozilla Thunderbird ESR (dsb) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (el) | 153.2.0 | Mozilla Thunderbird ESR (el) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (en-CA) | 153.2.0 | Mozilla Thunderbird ESR (en-CA) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (en-GB) | 153.2.0 | Mozilla Thunderbird ESR (en-GB) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (en-US) | 153.2.0 | Mozilla Thunderbird ESR (en-US) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (es-AR) | 153.2.0 | Mozilla Thunderbird ESR (es-AR) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (es-ES) | 153.2.0 | Mozilla Thunderbird ESR (es-ES) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (es-MX) | 153.2.0 | Mozilla Thunderbird ESR (es-MX) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (et) | 153.2.0 | Mozilla Thunderbird ESR (et) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (eu) | 153.2.0 | Mozilla Thunderbird ESR (eu) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (fi) | 153.2.0 | Mozilla Thunderbird ESR (fi) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (fr) | 153.2.0 | Mozilla Thunderbird ESR (fr) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (fy-NL) | 153.2.0 | Mozilla Thunderbird ESR (fy-NL) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (ga-IE) | 153.2.0 | Mozilla Thunderbird ESR (ga-IE) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (gd) | 153.2.0 | Mozilla Thunderbird ESR (gd) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (gl) | 153.2.0 | Mozilla Thunderbird ESR (gl) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (he) | 153.2.0 | Mozilla Thunderbird ESR (he) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (hr) | 153.2.0 | Mozilla Thunderbird ESR (hr) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (hsb) | 153.2.0 | Mozilla Thunderbird ESR (hsb) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (hu) | 153.2.0 | Mozilla Thunderbird ESR (hu) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (hy-AM) | 153.2.0 | Mozilla Thunderbird ESR (hy-AM) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (id) | 153.2.0 | Mozilla Thunderbird ESR (id) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (is) | 153.2.0 | Mozilla Thunderbird ESR (is) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (it) | 153.2.0 | Mozilla Thunderbird ESR (it) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (ja) | 153.2.0 | Mozilla Thunderbird ESR (ja) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (ka) | 153.2.0 | Mozilla Thunderbird ESR (ka) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (kab) | 153.2.0 | Mozilla Thunderbird ESR (kab) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (kk) | 153.2.0 | Mozilla Thunderbird ESR (kk) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (ko) | 153.2.0 | Mozilla Thunderbird ESR (ko) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (lt) | 153.2.0 | Mozilla Thunderbird ESR (lt) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (lv) | 153.2.0 | Mozilla Thunderbird ESR (lv) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (ms) | 153.2.0 | Mozilla Thunderbird ESR (ms) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (nb-NO) | 153.2.0 | Mozilla Thunderbird ESR (nb-NO) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (nl) | 153.2.0 | Mozilla Thunderbird ESR (nl) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (nn-NO) | 153.2.0 | Mozilla Thunderbird ESR (nn-NO) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (pa-IN) | 153.2.0 | Mozilla Thunderbird ESR (pa-IN) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (pl) | 153.2.0 | Mozilla Thunderbird ESR (pl) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (pt-BR) | 153.2.0 | Mozilla Thunderbird ESR (pt-BR) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (pt-PT) | 153.2.0 | Mozilla Thunderbird ESR (pt-PT) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (rm) | 153.2.0 | Mozilla Thunderbird ESR (rm) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (ro) | 153.2.0 | Mozilla Thunderbird ESR (ro) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (ru) | 153.2.0 | Mozilla Thunderbird ESR (ru) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (sk) | 153.2.0 | Mozilla Thunderbird ESR (sk) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (sl) | 153.2.0 | Mozilla Thunderbird ESR (sl) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (sq) | 153.2.0 | Mozilla Thunderbird ESR (sq) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (sr) | 153.2.0 | Mozilla Thunderbird ESR (sr) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (sv-SE) | 153.2.0 | Mozilla Thunderbird ESR (sv-SE) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (th) | 153.2.0 | Mozilla Thunderbird ESR (th) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (tr) | 153.2.0 | Mozilla Thunderbird ESR (tr) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (uk) | 153.2.0 | Mozilla Thunderbird ESR (uk) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (uz) | 153.2.0 | Mozilla Thunderbird ESR (uz) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (vi) | 153.2.0 | Mozilla Thunderbird ESR (vi) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (zh-CN) | 153.2.0 | Mozilla Thunderbird ESR (zh-CN) 153.2.0 | Sep 1, 2026 |
| Mozilla Thunderbird ESR (zh-TW) | 153.2.0 | Mozilla Thunderbird ESR (zh-TW) 153.2.0 | Sep 1, 2026 |
| macOS | |||
| Mozilla Thunderbird | 155.0 | Mozilla Thunderbird 155.0 | Aug 28, 2026 |
| Linux | |||
| MozillaThunderbird · sles 15.7 | 153.2.0-150400.13.3.1 | SUSE-SU-2026:4268-1 | Sep 18, 2026 |
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