CVE-2026-113869
Received Received - Intake

Thunderbird Use-After-Free in S/MIME Decryption

Publication date: 2026-10-20

Last updated on: 2026-10-20

Assigner: Mozilla Corporation

Description
When Thunderbird asked for a security device password (for example a smartcard PIN or the Primary Password) while decrypting an S/MIME message, the message load could finish or be cancelled while the prompt was open. This freed the message decoder while it was still in use, causing a use-after-free and a potentially exploitable crash. This vulnerability was fixed in Thunderbird 158.0.1.

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Meta Information

Published
2026-10-20
Last Modified
2026-10-20
Generated
2026-10-21
AI Q&A
2026-10-20
EPSS Evaluated
N/A
NVD
CVE-2026-113869
EUVD
EUVD-2026-105296

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
mozilla thunderbird 158.0.1

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-416 The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.

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Executive Summary

This is a use-after-free vulnerability in Thunderbird's S/MIME decryption process. When Thunderbird asks for a security device password during decryption, the message load might finish or be canceled while the password prompt is still open. This frees the message decoder while it is still in use, causing a use-after-free error that could lead to a crash.

Impact Analysis

This vulnerability could allow an attacker to cause Thunderbird to crash by exploiting the use-after-free condition. If successful, this might lead to arbitrary code execution, potentially compromising the user's system or data.

Mitigation Strategies

Update Thunderbird to version 158.0.1 or later to address the vulnerability. Disable S/MIME decryption if not required or restrict access to sensitive messages until patched.

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