CVE-2026-113869: Use-after-free in S/MIME decryption during a security device password prompt

Published Oct 20, 2026
·
Updated

When Thunderbird asked for a security device password (for example a smartcard PIN or the Primary Password) while decrypting an S/MIME message, the message load could finish or be cancelled while the prompt was open. This freed the message decoder while it was still in use, causing a use-after-free and a potentially exploitable crash. This vulnerability was fixed in Thunderbird 158.0.1 and Thunderbird 153.6.

Affected Software

8 affected componentsFixes available
Mozilla Thunderbird<158.0.1
Mozilla Thunderbird<153.6
153.6
ubuntu/thunderbird*
ubuntu/thunderbird*
ubuntu/thunderbird*
ubuntu/thunderbird*
Mozilla Thunderbird<158.0.1
158.0.1
debian/thunderbird
1:140.12.0esr-1~deb12u11:153.6.0esr-1~deb12u11:140.12.0esr-1~deb13u11:153.5.1esr-1~deb13u21:153.5.0esr-11:153.6.0esr-1

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 153.6
  2. Upgrade

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

    Fixed in 158.0.1
  3. Upgrade

    Upgrade debian/thunderbird to a version that resolves this vulnerability.

    Fixed in 1:140.12.0esr-1~deb12u1Fixed in 1:153.6.0esr-1~deb12u1Fixed in 1:140.12.0esr-1~deb13u1Fixed in 1:153.5.1esr-1~deb13u2Fixed in 1:153.5.0esr-1Fixed in 1:153.6.0esr-1
  4. Upgrade

    Upgrade Thunderbird to a version that resolves this vulnerability.

    Fixed in 158.0.1
  5. Upgrade

    Upgrade Thunderbird to a version that resolves this vulnerability.

    Fixed in 153.6

Event History

Oct 20, 2026
CVE Published
via Mozilla·12:00 AM
Data Sourced
via Mozilla·12:00 AM
DescriptionSeverityAffected Software
Data Sourced
via Ubuntu·12:00 AM
RemedyDescriptionSeverityAffected Software
CVE Published
via MITRE·07:14 PM
Data Sourced
via MITRE·07:14 PM
Description
Data Sourced
via Red Hat·07:31 PM
DescriptionSeverityAffected Software
Data Sourced
via OSV·08:17 PM
DescriptionSeverityAffected Software
Data Sourced
via NVD·08:17 PM
DescriptionSeverityWeakness

Parent advisories

This vulnerability appears in the following advisories.

Peer vulnerabilities

Found alongside the following vulnerabilities.

Frequently Asked Questions

1

Who is exposed to this issue?

Thunderbird users who decrypt S/MIME messages and may be prompted for a security device password, such as a smartcard PIN or Primary Password, are exposed. Exploitation requires the affected decryption flow to be active.

2

What must occur for the use-after-free condition to be triggered?

While Thunderbird is prompting for the security device password during S/MIME decryption, the message load must finish or be cancelled before the prompt is closed. That can free the message decoder while it is still in use.

3

Is authentication or user interaction required?

The CVSS vector indicates low privileges are required and no separate user interaction is required. The relevant password prompt occurs as part of Thunderbird's S/MIME decryption process.

4

What version contains the fix?

The issue was fixed in Thunderbird 158.0.1.

Company

Resources

Contact

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