Description
Thunderbird ignored the configuration to require STARTTLS security for an SMTP connection. A MITM could perform a downgrade attack to intercept transmitted messages, or could take control of the authenticated session to execute SMTP commands chosen by the MITM. If an unprotected authentication method was configured, the MITM could obtain the authentication credentials, too. This vulnerability affects Thunderbird < 91.2.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mozilla | Thunderbird | unspecified – < 91.2 | 91.2 |
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 | 1:91.2.1-1 | — |
| Debian 13 | thunderbird | 1:91.2.1-1 | — |
| Debian 12 | thunderbird | 1:91.2.1-1 | — |
| 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 | 1:91.3.1+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 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8 | thunderbird | 91.2.0-1.el8_4 | RHSA-2021:3838 |
| RHEL 7 | thunderbird | 91.2.0-1.el7_9 | RHSA-2021:3841 |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8.2 EUS | thunderbird | 91.2.0-1.el8_2 | RHSA-2021:3839 |
| RHEL 8.1 EUS | thunderbird | 91.2.0-1.el8_1 | RHSA-2021:3840 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 8 | thunderbird | 91.2.0-1.el8_4 | RLSA-2021:3838 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP3 | MozillaThunderbird | 91.4.0-8.45.2 | SUSE-SU-2021:4150-1 |
| SLES 15 SP2 | MozillaThunderbird | 91.4.0-8.45.2 | SUSE-SU-2021:4150-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Leap 15.3 | MozillaThunderbird | 91.4.0-8.45.2 | openSUSE-SU-2021:4150-1 |
| openSUSE Leap 15.2 | MozillaThunderbird | 91.4.0-lp152.2.52.1 | openSUSE-SU-2021:1635-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.23 | thunderbird | 91.3.2-r0 | — |
| Alpine v3.22 | thunderbird | 91.3.2-r0 | — |
| Alpine v3.21 | thunderbird | 91.3.2-r0 | — |
| Alpine v3.20 | thunderbird | 91.3.2-r0 | — |
| Alpine v3.19 | thunderbird | 91.3.2-r0 | — |
Show 3 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.18 | thunderbird | 91.3.2-r0 | — |
| Alpine v3.17 | thunderbird | 91.3.2-r0 | — |
| Alpine v3.16 | thunderbird | 91.3.2-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2 | thunderbird | 91.6.0-1.amzn2.0.1 | ALAS2-2022-1818 |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 8 | thunderbird | 91.2.0-1.0.1.el8_4 | ELSA-2021-3838 |
| Oracle Linux 7 | thunderbird | 91.2.0-1.0.1.el7_9 | ELSA-2021-3841 |
Advisories 14
- RHSA-2021:3841 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- 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
- RLSA-2021:3838 Important: thunderbird security update Rocky Linux Security Advisories · Feb 4, 2026
- SUSE-SU-2021:4150-1 Security update for MozillaThunderbird SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2021:4150-1 Security update for MozillaThunderbird SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2021:1635-1 Security update for MozillaThunderbird SUSE / openSUSE Security Updates · Feb 4, 2026
- RHSA-2021:3840 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2021:3839 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2021:3838 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- ALAS2-2022-1818 Important: thunderbird security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Aug 21, 2022
- ELSA-2021-3841 Important: thunderbird security update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Oct 25, 2021
- ELSA-2021-3838 Important: thunderbird security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Oct 15, 2021