# Mozilla Thunderbird (en-US) 91.0.3

Mozilla Thunderbird (en-US) 91.0.3, released August 24, 2021, fixes 9 CVEs in Mozilla Thunderbird (en-US). None of them is reported as exploited. Patch Radar priority: High. The latest Mozilla Thunderbird (en-US) is 159.0, which also fixes every one of these CVEs.

- Web page: https://patchblox.com/security/fix/windows-app/mozilla.thunderbird-91.0.3
- Platform: Windows apps
- Released: Aug 24, 2021
- Priority: High (Closes CVE-2021-29985, high severity)
- CVEs: 9, exploited: 0, on CISA KEV: 0
- Superseded by: [Mozilla Thunderbird (en-US) 159.0](https://patchblox.com/security/data/product/windows-app/mozilla-thunderbird-en-us.md), the latest version, which also fixes every CVE listed here

## Applies to

| Product | Release | Fixed in |
|---|---|---|
| [Mozilla Thunderbird (en-US)](https://patchblox.com/security/data/product/windows-app/mozilla-thunderbird-en-us.md) |  | 91.0.3 |

## CVEs this fix closes

| CVE | Priority | Title | CVSS | EPSS | Exploitation |
|---|---|---|---:|---:|---|
| [CVE-2021-29985](https://patchblox.com/security/data/cve/CVE-2021-29985.md) | High | Firefox ESR and 3 others: A use-after-free vulnerability in media channels could have led to memory corruption and a potentially… | 8.8 | 0.0145 |  |
| [CVE-2021-29980](https://patchblox.com/security/data/cve/CVE-2021-29980.md) | High | Firefox ESR and 3 others: Uninitialized memory in a canvas object could have caused an incorrect free() leading to memory corruption… | 8.8 | 0.0140 |  |
| [CVE-2021-29984](https://patchblox.com/security/data/cve/CVE-2021-29984.md) | High | Firefox ESR and 3 others: Instruction reordering resulted in a sequence of instructions that would cause an object to be incorrectly… | 8.8 | 0.0139 |  |
| [CVE-2021-29988](https://patchblox.com/security/data/cve/CVE-2021-29988.md) | High | Firefox ESR and 3 others: Firefox incorrectly treated an inline list-item element as a block element, resulting in an out of bounds… | 8.8 | 0.0138 |  |
| [CVE-2021-29989](https://patchblox.com/security/data/cve/CVE-2021-29989.md) | High | Firefox ESR and 3 others: Mozilla developers reported memory safety bugs present in Firefox 90 and Firefox ESR 78.12. | 8.8 | 0.0127 |  |
| [CVE-2021-38493](https://patchblox.com/security/data/cve/CVE-2021-38493.md) | High | Mozilla Firefox ESR and 3 others: Mozilla developers reported memory safety bugs present in Firefox 91 and Firefox ESR 78.13. | 8.8 | 0.0125 |  |
| [CVE-2021-29981](https://patchblox.com/security/data/cve/CVE-2021-29981.md) | High | Firefox ESR and 3 others: An issue present in lowering/register allocation could have led to obscure but deterministic register… | 8.8 | 0.0101 |  |
| [CVE-2021-29991](https://patchblox.com/security/data/cve/CVE-2021-29991.md) | High | Firefox ESR and 3 others: Firefox incorrectly accepted a newline in a HTTP/3 header, interpretting it as two separate headers. | 8.1 | 0.0091 |  |
| [CVE-2021-29982](https://patchblox.com/security/data/cve/CVE-2021-29982.md) | Routine | Firefox ESR and 3 others: Due to incorrect JIT optimization, we incorrectly interpreted data from the wrong type of object, resulting… | 6.5 | 0.0112 |  |

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Data as of 2026-11-10T07:50:38Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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