Description
When receiving an OpenPGP/MIME signed email message that contains an additional outer MIME message layer, for example a message footer added by a mailing list gateway, Thunderbird only considered the inner signed message for the signature validity. This gave the false impression that the additional contents were also covered by the digital signature. Starting with Thunderbird version 91.4.1, only the signature that belongs to the top level MIME part will be considered for the displayed status. This vulnerability affects Thunderbird < 91.4.1.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mozilla | Thunderbird | unspecified – < 91.4.1 | 91.4.1 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | thunderbird | 1:91.4.1-1 | — |
| Debian 13 | thunderbird | 1:91.4.1-1 | — |
| Debian 12 | thunderbird | 1:91.4.1-1 | — |
| Debian 11 | thunderbird | 1:91.4.1-1~deb11u1 | DSA-5034-1 |
| Debian 10 | thunderbird | 1:91.4.1-1~deb10u1 | DSA-5034-1 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 9 | thunderbird | 1:91.4.1-1~deb9u1 | DLA-2874-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 22.04 LTS | thunderbird | 1:91.5.0+build1-0ubuntu1 | — |
| Ubuntu 20.04 LTS | thunderbird | 1:91.5.0+build1-0ubuntu0.20.04.1 | USN-5248-1 |
| Ubuntu 18.04 LTS | thunderbird | 1:91.5.0+build1-0ubuntu0.18.04.1 | USN-5248-1 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP3 | MozillaThunderbird | 91.4.1-8.48.1 | SUSE-SU-2022:0058-1 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SUSE Package Hub 15 SP3 | zabbix | 4.0.38-bp153.2.3.1 | openSUSE-SU-2022:0058-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | MozillaThunderbird | 91.4.1-1.1 | openSUSE-SU-2024:11698-1 |
| openSUSE Leap 15.3 | MozillaThunderbird | 91.4.1-8.48.1 | openSUSE-SU-2022:0058-1 |
| openSUSE Leap 15.3 | zabbix | 4.0.38-bp153.2.3.1 | openSUSE-SU-2022:0058-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.23 | thunderbird | 91.4.1-r0 | — |
| Alpine v3.22 | thunderbird | 91.4.1-r0 | — |
| Alpine v3.21 | thunderbird | 91.4.1-r0 | — |
| Alpine v3.20 | thunderbird | 91.4.1-r0 | — |
| Alpine v3.19 | thunderbird | 91.4.1-r0 | — |
Show 3 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.18 | thunderbird | 91.4.1-r0 | — |
| Alpine v3.17 | thunderbird | 91.4.1-r0 | — |
| Alpine v3.16 | thunderbird | 91.4.1-r0 | — |
Advisories 6
- USN-5248-1 thunderbird vulnerabilities Ubuntu Security Notices (USN) · Apr 27, 2026
- DSA-5034-1 thunderbird - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-2874-1 thunderbird - security update Debian Security (DSA / DLA) · Mar 9, 2026
- SUSE-SU-2022:0058-1 Security update for MozillaThunderbird SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2024:11698-1 MozillaThunderbird-91.4.1-1.1 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2022:0058-1 Security update for MozillaThunderbird SUSE / openSUSE Security Updates · Feb 4, 2026