CVE-2026-113866

Received Received - Intake

Thunderbird Exchange AutoDiscover Credential Exposure

Publication date: 2026-10-20

Last updated on: 2026-10-20

Assigner: Mozilla Corporation

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.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-10-20

Last Modified

2026-10-20

Generated

2026-10-21

AI Q&A

2026-10-21

EPSS Evaluated

N/A

NVD

CVE-2026-113866

EUVD

EUVD-2026-105293

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	thunderbird	158.0.1
mozilla	thunderbird	153.5.1

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-523	Login pages do not use adequate measures to protect the user name and password while they are in transit from the client to the server.

Attack-Flow Graph

Executive Summary

This vulnerability occurs when setting up an Exchange account in Thunderbird. The software queries the domain's AutoDiscover service over unencrypted HTTP during setup. A bug causes the user's entered credentials to be sent in this unencrypted request, allowing network attackers to intercept and obtain the password.

Impact Analysis

If you use Thunderbird to set up an Exchange account, an attacker on the same network could capture your account password during the setup process. This could lead to unauthorized access to your email or other services using the same credentials.

Mitigation Strategies

Update Thunderbird to version 158.0.1 or 153.5.1 or later to address the vulnerability.

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