Mozilla Thunderbird up to 153.1/154 Attachment Hostname Matching incorrect regex

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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6.0$5k-$25k0.00+

Summaryinfo

A vulnerability, which was classified as critical, was found in Mozilla Thunderbird up to 153.1/154. This affects an unknown part of the component Attachment Hostname Matching. The manipulation results in incorrect regex. This vulnerability was named CVE-2026-84642. The attack may be performed from remote. There is no available exploit.

Detailsinfo

A vulnerability, which was classified as critical, was found in Mozilla Thunderbird up to 153.1/154. Affected is some unknown functionality of the component Attachment Hostname Matching. The manipulation with an unknown input leads to a incorrect regex vulnerability. CWE is classifying the issue as CWE-185. The product specifies a regular expression in a way that causes data to be improperly matched or compared. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

The values of the mail.allowed_attachment_hostnames advanced config setting were used in a regular expression without escaping. For some possible valid hostnames, this could allow certain unintended hostnames to also match and serve remote attachments. This vulnerability was fixed in Thunderbird 155 and Thunderbird 153.2.

The advisory is available at bugzilla.mozilla.org. This vulnerability is traded as CVE-2026-84642 since 09/01/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Successful exploitation requires user interaction by the victim. The technical details are unknown and an exploit is not available. The structure of the vulnerability defines a possible price range of USD $5k-$25k at the moment (estimation calculated on 09/01/2026).

Upgrading to version 153.2 or 155 eliminates this vulnerability.

If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.3
VulDB Meta Temp Score: 6.0

VulDB Base Score: 6.3
VulDB Temp Score: 6.0
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

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

Exploitinginfo

Class: Incorrect regex
CWE: CWE-185 / CWE-697
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
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 153.2/155

Timelineinfo

09/01/2026 Advisory disclosed
09/01/2026 +0 days CVE reserved
09/01/2026 +0 days VulDB entry created
09/01/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: mozilla.org

Advisory: bugzilla.mozilla.org
Status: Confirmed

CVE: CVE-2026-84642 (🔒)
GCVE (CVE): GCVE-0-2026-84642
GCVE (VulDB): GCVE-100-397938

Entryinfo

Created: 09/01/2026 23:53
Changes: 09/01/2026 23:53 (57)
Complete: 🔍
Cache ID: 216::103

If you want to get best quality of vulnerability data, you may have to visit VulDB.

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