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CVE-2026-113867

9.1 · CRITICAL

Thunderbird did not escape attribute values when serializing outgoing XMPP stanzas.

Published Oct 20, 2026CWE-116EPSS 0.40%

Overview

CVE-2026-113867 is a critical-severity vulnerability. It was published on October 20, 2026 and has a CVSS 3.1 base score of 9.1 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.1, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refbugzilla.mozilla.org/show_bug.cgi?id=2080073Refwww.mozilla.org/security/advisories/mfsa2026-114/Refwww.mozilla.org/security/advisories/mfsa2026-115/

How CyberStrike helps

Frequently asked questions

What is CVE-2026-113867?

CVE-2026-113867 is a critical-severity vulnerability. It was published on October 20, 2026 and has a CVSS 3.1 base score of 9.1 (CRITICAL).

How severe is CVE-2026-113867?

This vulnerability has a CVSS 3.1 base score of 9.1, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-113867?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-113867?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-113867 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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