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CVE-2026-92240

Mozilla Thunderbird out-of-bounds read

9.1 CRITICALEPSS 0.63%
  1. Published15 Sept 2026

Description

A malicious or compromised IMAP server can trigger an out-of-bounds read in the IMAP response parser by sending an untagged '* ID' response, crashing Thunderbird. The affected parsing path is reachable before authentication. This vulnerability was fixed in Thunderbird 156, Thunderbird 140.16, and Thunderbird 153.3.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Affected products

Mozilla Thunderbird≥ 141.0 < 153.3.0 · ≥ 154.0 < 156.0 · < 140.16.0

Remediation

Fixed in
Mozilla Thunderbird≥ 153.3.0

References

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Frequently asked

Is CVE-2026-92240 being actively exploited?

CVE-2026-92240 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.63%.

How severe is CVE-2026-92240?

CVE-2026-92240 has a CVSS 3.1 base score of 9.1, rated critical. EPSS estimates a 0.63% probability of exploitation.

Which products are affected by CVE-2026-92240?

Affected products include Mozilla Thunderbird.

How do I fix CVE-2026-92240?

Upgrade affected software to a fixed version, for example Mozilla Thunderbird 153.3.0 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.