Mozilla Thunderbird up to 140.14/153.1/154 IMAP ID prefs.js use after free

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-$25k0.94

Summaryinfo

A vulnerability, which was classified as critical, has been found in Mozilla Thunderbird up to 140.14/153.1/154. Affected by this issue is some unknown functionality of the file prefs.js of the component IMAP ID Handler. The manipulation leads to use after free. This vulnerability is uniquely identified as CVE-2026-84641. The attack is possible to be carried out remotely. No exploit exists.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Mozilla Thunderbird up to 140.14/153.1/154. This issue affects an unknown functionality of the file prefs.js of the component IMAP ID Handler. The manipulation with an unknown input leads to a use after free vulnerability. Using CWE to declare the problem leads to CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

A malicious IMAP server can trigger use-after-free and heap-memory disclosure by sending a crafted ID response. Heap contents can ultimately be persisted to prefs.js. This vulnerability was fixed in Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.

The advisory is shared at bugzilla.mozilla.org. The identification of this vulnerability is CVE-2026-84641 since 09/01/2026. The exploitation is known to be easy. The attack may be initiated remotely. Technical details are known, but no exploit is available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 09/02/2026).

Upgrading to version 140.15, 153.2 or 155 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-69710). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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

Exploitinginfo

Class: Use after free
CWE: CWE-416 / CWE-119
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 140.15/153.2/155

Timelineinfo

09/01/2026 Advisory disclosed
09/01/2026 +0 days CVE reserved
09/01/2026 +0 days VulDB entry created
09/02/2026 +1 days VulDB entry last update

Sourcesinfo

Vendor: mozilla.org

Advisory: bugzilla.mozilla.org
Status: Confirmed

CVE: CVE-2026-84641 (🔒)
GCVE (CVE): GCVE-0-2026-84641
GCVE (VulDB): GCVE-100-397937
EUVD: 🔒

Entryinfo

Created: 09/01/2026 23:52
Updated: 09/02/2026 02:03
Changes: 09/01/2026 23:52 (58), 09/02/2026 02:03 (1)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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