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CVE-2026-113866

Medium

Description

When setting up an account, Thunderbird's Exchange AutoDiscover lookup also queried the domain's AutoDiscover service over plain HTTP. Due to a bug, that unencrypted request included the credentials the user had entered, allowing a network attacker to obtain the user's password. This vulnerability was fixed in Thunderbird 158.0.1 and Thunderbird 153.5.1.

SeverityMedium
CVSS5.9
Exploit probability—
ProductThunderbird
PublishedOct 20, 2026
First seenOct 20, 2026
Weakness typeCWE-523CWE-523

How to fix

Update
  • Thunderbird158.0.1, 153.5.1 or later

Affected products

ProductAffected versionsFixed in
ThunderbirdNo range specified158.0.1, 153.5.1

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