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VulnerabilityPublished

CVE-2026-126136: Mozilla Thunderbird · OAuth2 access token could be sent over an unencrypted connection with Exchange accounts

Affects Mozilla ThunderbirdSource CVE Database V5

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Not known to be exploited · fixed in 153.7 : patch Mozilla Thunderbird soon.

Data as of 10 Nov 2026, 20:34 UTC

Severity
High

Rated High by Threat Radar's AI analysis · CVSS not yet scored by NVD

Thin evidence

One scorer or none
Patch
Available – fixed in 153.7

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 10 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 10 Nov 2026.

What to do

AI-suggested

This vulnerability has been fixed in Thunderbird version 160. Users and administrators should upgrade to Thunderbird 160 or later to ensure tokens are not sent over unencrypted connections. No additional mitigation is required once the update is applied.

Description

For Exchange accounts using EWS or Microsoft Graph with OAuth2 authentication, Thunderbird sent the OAuth2 access token to the server even when the configured server URL used unencrypted HTTP. An attacker able to observe network traffic could obtain the token and use it to access the user's mailbox until the token expired. An attacker positioned on the network during account setup could cause such a URL to be configured. This vulnerability was fixed in Thunderbird 160 and Thunderbird 153.7.

References

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