CVE-2026-84641

7.5 HIGH 0.3% exploit odds Fix listed Memory safety Browser & mail

What it 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.

At a glance

Exploitability: Can be exploited over the network without logging in. High risk of data exposure.
Exploit odds: 0.3% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-09-01 22:17 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-09-03 19:01 UTC Last updatedMost recent change to the record

Details

Published: 2026-09-01 22:17 UTC
Last modified: 2026-09-03 19:01 UTC
Exploit probability: 0.3% · EPSS, next 30 days
Weakness: CWE-416 · Use after free
Record status: Analyzed

Affected

Mozilla Thunderbird < 140.15.0
Mozilla Thunderbird < 153.2.0
Mozilla Thunderbird < 155.0

Attack profile CVSS 3.1 · 7.5

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: None
Availability: None

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

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Fix and advisories

References

NVD record · CVE.org record