Mozilla Thunderbird up to 158.0.0 AutoDiscover service cleartext transmission

CVSS Meta Temp Score
CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.
Current Exploit Price (≈)
Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.
CTI Interest Score
Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
3.6$0-$5k0.00

Summaryinfo

A vulnerability was found in Mozilla Thunderbird up to 158.0.0. It has been declared as problematic. This affects an unknown part of the component AutoDiscover service. Executing a manipulation can lead to cleartext transmission. The identification of this vulnerability is CVE-2026-113866. The attack may be launched remotely. There is no exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic was found in Mozilla Thunderbird up to 158.0.0. This vulnerability affects some unknown processing of the component AutoDiscover service. The manipulation with an unknown input leads to a cleartext transmission vulnerability. The CWE definition for the vulnerability is CWE-319. The product transmits sensitive or security-critical data in cleartext in a communication channel that can be sniffed by unauthorized actors. As an impact it is known to affect confidentiality. CVE summarizes:

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.

The advisory is available at bugzilla.mozilla.org. This vulnerability was named CVE-2026-113866 since 10/20/2026. The exploitation appears to be difficult. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. The technical details are unknown and an exploit is not available. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 10/20/2026). This vulnerability is assigned to T1040 by the MITRE ATT&CK project.

Upgrading to version 158.0.1 eliminates this vulnerability.

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Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 3.7
VulDB Meta Temp Score: 3.6

VulDB Base Score: 3.7
VulDB Temp Score: 3.6
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Cleartext transmission
CWE: CWE-319 / CWE-310
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Thunderbird 158.0.1

Timelineinfo

10/20/2026 Advisory disclosed
10/20/2026 +0 days CVE reserved
10/20/2026 +0 days VulDB entry created
10/20/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: mozilla.org

Advisory: bugzilla.mozilla.org
Status: Confirmed

CVE: CVE-2026-113866 (🔒)
GCVE (CVE): GCVE-0-2026-113866
GCVE (VulDB): GCVE-100-422974

Entryinfo

Created: 10/20/2026 21:37
Changes: 10/20/2026 21:37 (57)
Complete: 🔍
Cache ID: 216::103

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