CVE-2026-92240: Out-of-bounds read in IMAP response parser

Published Sep 15, 2026
·
Updated

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.

Affected Software

3 affected componentsFixes available
Mozilla Thunderbird<140.16
Mozilla Thunderbird<156
156
Mozilla Thunderbird<140.16
140.16

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 156
  2. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 140.16
  3. Upgrade

    Upgrade Thunderbird to a version that resolves this vulnerability.

    Fixed in 140.16

Event History

Sep 15, 2026
CVE Published
via Mozilla·12:00 AM
Data Sourced
via Mozilla·12:00 AM
DescriptionSeverityAffected Software
Updated
via Mozilla·12:00 AM
Affected Software
CVE Published
via MITRE·07:42 PM
Data Sourced
via MITRE·07:42 PM
Description

Parent advisories

This vulnerability appears in the following advisories.

Peer vulnerabilities

Found alongside the following vulnerabilities.

Frequently Asked Questions

1

Who can exploit this issue?

An attacker controlling, impersonating, or able to alter traffic from an IMAP server can send the malformed untagged response. Because the vulnerable parser is reached before authentication, the client does not need to authenticate to the server first.

2

What is the practical impact?

The supplied information identifies a client crash caused by an out-of-bounds read. It does not establish code execution, data disclosure, or any impact beyond crashing Thunderbird.

3

Which Thunderbird version contains the fix?

The issue was fixed in Thunderbird 140.16.

Company

Resources

Contact

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