CVE-2026-110247: Integer overflow in libmime buffer growth could lead to heap corruption

Published Oct 13, 2026
·
Updated

Several buffer-growth sites in libmime performed size arithmetic in 32-bit types without overflow checks. On a sufficiently large message the growth guard could fail open, or the buffer could be reallocated smaller than required, and a subsequent memcpy would then write attacker-controlled data across adjacent heap allocations.

Affected Software

2 affected componentsFixes available
Mozilla Thunderbird<158
Mozilla Thunderbird<158
158

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 158
  2. Upgrade

    Upgrade Thunderbird to a version that resolves this vulnerability.

    Fixed in 158

Event History

Oct 13, 2026
CVE Published
via Mozilla·12:00 AM
Data Sourced
via Mozilla·12:00 AM
DescriptionSeverityAffected Software
CVE Published
via MITRE·06:08 PM
Data Sourced
via MITRE·06:08 PM
Description

Parent advisories

This vulnerability appears in the following advisories.

Peer vulnerabilities

Found alongside the following vulnerabilities.

Frequently Asked Questions

1

Which Thunderbird versions need remediation?

The issue was fixed in Thunderbird 158. The provided information does not identify the first affected version, so deployments should verify whether they are running a release earlier than 158.

2

What would an attacker need to exploit this issue?

An attacker would need to cause Thunderbird's libmime component to process a sufficiently large message containing attacker-controlled data. The vulnerable buffer-growth arithmetic can result in a smaller-than-required allocation followed by a memcpy that overwrites adjacent heap memory.

Company

Resources

Contact

SecAlerts Pty Ltd.
132 Wickham Terrace
Fortitude Valley,
QLD 4006, Australia
info@secalerts.co
By using SecAlerts services, you agree to our services end-user license agreement. This website is safeguarded by reCAPTCHA and governed by the Google Privacy Policy and Terms of Service. All names, logos, and brands of products are owned by their respective owners, and any usage of these names, logos, and brands for identification purposes only does not imply endorsement. If you possess any content that requires removal, please get in touch with us.
© 2026 SecAlerts Pty Ltd.
ABN: 70 645 966 203, ACN: 645 966 203