# CVE-2026-113867: thunderbird: Thunderbird did not escape attribute values when serializing outgoing XMPP stanzas

CVE-2026-113867 is fixed in thunderbird on 1 platform, first by DEBIAN-CVE-2026-113867, released October 27, 2026. It is not reported as exploited. Patch Radar priority: Urgent.

- Web page: https://patchblox.com/security/cve/CVE-2026-113867
- Priority: Urgent
- CVSS: 9.1 (critical)
- EPSS: 0.0040
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 20, 2026

## Description

Thunderbird did not escape attribute values when serializing outgoing XMPP stanzas. Because values from incoming requests were echoed back in automatic replies, a remote XMPP user could send a crafted request that caused Thunderbird to inject arbitrary stanzas into the user's connection, which the server would then process as if sent by the user. This could be used to send messages or change contact and subscription settings on behalf of the user, without any interaction. This bug only affects Thunderbird's chat feature with XMPP accounts. This vulnerability was fixed in Thunderbird 158.0.1 and Thunderbird 153.5.1.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | thunderbird Debian 12.15 (bookworm) | 1:153.5.1esr-1~deb12u1 | [DEBIAN-CVE-2026-113867](https://patchblox.com/security/data/fix/linux/debian-cve-2026-113867.md) | Oct 27, 2026 |
| Linux | thunderbird Debian 13.5 (trixie) | 1:153.5.1esr-1~deb13u1 | [DEBIAN-CVE-2026-113867](https://patchblox.com/security/data/fix/linux/debian-cve-2026-113867.md) | Oct 27, 2026 |

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Data as of 2026-11-10T01:44:33Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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