A malicious mail server could send malformed strings with negative lengths, causing the parser to read memory outside the buffer. If a mail server or connection to a mail server were compromised, an attacker could cause the parser to malfunction, potentially crashing Thunderbird or leaking sensitive data. This vulnerability affects Thunderbird < 149 and Thunderbird < 140.9.

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Fixes

Solution

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Workaround

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History

Wed, 25 Mar 2026 17:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-126
Metrics cvssV3_1

{'score': 7.4, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:H'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Wed, 25 Mar 2026 12:00:00 +0000

Type Values Removed Values Added
First Time appeared Mozilla
Mozilla thunderbird
Vendors & Products Mozilla
Mozilla thunderbird

Tue, 24 Mar 2026 20:30:00 +0000

Type Values Removed Values Added
Description A malicious mail server could send malformed strings with negative lengths, causing the parser to read memory outside the buffer. If a mail server or connection to a mail server were compromised, an attacker could cause the parser to malfunction, potentially crashing Thunderbird or leaking sensitive data. This vulnerability affects Thunderbird < 149 and Thunderbird < 140.9.
Title Out of bounds read in IMAP parsing
References

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cve-icon MITRE

Status: PUBLISHED

Assigner: mozilla

Published:

Updated: 2026-03-25T16:24:50.635Z

Reserved: 2026-03-18T10:03:43.909Z

Link: CVE-2026-4371

cve-icon Vulnrichment

Updated: 2026-03-25T16:24:43.854Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-03-24T21:16:29.583

Modified: 2026-03-25T17:17:09.717

Link: CVE-2026-4371

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-03-25T11:45:52Z

Weaknesses

No weakness.