# CVE-2026-113867: Thunderbird XMPP stanza injection in chat

Source: https://junglewise.ai/threats/cve-2026-113867-thunderbird-did-not-escape-attribute-values-when-serializing  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-20. Updated: 2026-10-20  
License: CC BY 4.0 with a link back

CVE-2026-113867 · Severity: info · Published 2026-10-20

Thunderbird's XMPP chat feature fails to properly escape attribute values when processing incoming messages, allowing a remote attacker to inject arbitrary stanzas into the user's connection. An attacker can send a crafted message that causes Thunderbird to execute commands on behalf of the user, such as sending messages or modifying contact settings, without any user interaction required.

Technologies: [Mozilla Thunderbird](https://junglewise.ai/threats/technologies/thunderbird). Vendors: [Mozilla](https://junglewise.ai/threats/vendors/mozilla).

## Quick answers

**Is CVE-2026-113867 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-113867 being exploited in the wild.

**How severe is CVE-2026-113867?** Informational severity, published 20 October 2026.

**Which products and versions are affected?** Mozilla Thunderbird prior to 158.0.1 and 153.5.1.

**Is there a fix for CVE-2026-113867?** Yes: fixed in Thunderbird 158.0.1, 153.5.1. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-113867 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-113867?** Check whether you run Mozilla Thunderbird at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in Thunderbird 158.0.1, 153.5.1

## Technical details

Thunderbird's XMPP implementation does not escape attribute values when serializing outgoing stanzas; incoming request values are echoed back in automatic replies, enabling stanza injection. A remote XMPP user can craft a request that injects arbitrary stanzas processed by the server as legitimate user commands. This requires an active XMPP account and contact with the attacking user, but no user interaction.

## Affected products

- Mozilla Thunderbird prior to 158.0.1 and 153.5.1

## Timeline

- 2026-10-20: disclosed
- 2026-10-20: patched

## References

- [https://bugzilla.mozilla.org/show_bug.cgi?id=2080073](https://bugzilla.mozilla.org/show_bug.cgi?id=2080073)
- [https://www.mozilla.org/security/advisories/mfsa2026-114/](https://www.mozilla.org/security/advisories/mfsa2026-114/)

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