CVE-2025-0243: Memory safety bugs fixed in Firefox 134, Thunderbird 134, Firefox ESR 128.6, and Thunderbird 128.6

Published Jan 7, 2025
·
Updated

Memory safety bugs present in Firefox 133, Thunderbird 133, Firefox ESR 128.5, and Thunderbird 128.5. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 134, Firefox ESR 128.6, Thunderbird 134, and Thunderbird 128.6.

Other sources

Memory safety bugs present in Firefox 133, Thunderbird 133, Firefox ESR 128.5, and Thunderbird 128.5. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox < 134 and Firefox ESR < 128.6.

— Red Hat

Affected Software

22 affected componentsFixes available
Mozilla Thunderbird<134
134
Mozilla Firefox ESR<128.6
128.6
Mozilla Firefox<128.6.0
Mozilla Firefox<133.0
Mozilla Thunderbird<128.6.0
Mozilla Thunderbird>=129.0<134.0
ubuntu/mozjs52*
ubuntu/mozjs38*
ubuntu/firefox<134.0+build1-0ubuntu0.20.04.1
134.0+build1-0ubuntu0.20.04.1
ubuntu/mozjs68*
ubuntu/mozjs52*
ubuntu/mozjs102*
ubuntu/mozjs78*
ubuntu/mozjs91*
ubuntu/thunderbird<1:140.7.1+build1-0ubuntu0.22.04.1
1:140.7.1+build1-0ubuntu0.22.04.1
ubuntu/mozjs102*
ubuntu/mozjs115*
Mozilla Firefox<134
134
Mozilla Thunderbird<128.6
128.6
debian/firefox
159.0.1-1
debian/firefox-esr
140.12.0esr-1~deb12u1153.6.0esr-1~deb12u2140.15.0esr-1~deb13u1153.6.0esr-1~deb13u1153.5.1esr-1153.6.0esr-1
debian/thunderbird
1:140.12.0esr-1~deb12u11:153.6.0esr-1~deb12u21:140.12.0esr-1~deb13u11:153.6.0esr-1~deb13u11:153.5.0esr-11:153.6.0esr-1

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade Thunderbird to a version that resolves this vulnerability.

    Fixed in 134
  2. Upgrade

    Upgrade Firefox ESR to a version that resolves this vulnerability.

    Fixed in 128.6
  3. Upgrade

    Upgrade ubuntu/firefox to a version that resolves this vulnerability.

    Fixed in 134.0+build1-0ubuntu0.20.04.1
  4. Upgrade

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

    Fixed in 1:140.7.1+build1-0ubuntu0.22.04.1
  5. Upgrade

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

    Fixed in 134
  6. Upgrade

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

    Fixed in 128.6
  7. Upgrade

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

    Fixed in 159.0.1-1
  8. Upgrade

    Upgrade debian/firefox-esr to a version that resolves this vulnerability.

    Fixed in 140.12.0esr-1~deb12u1Fixed in 153.6.0esr-1~deb12u2Fixed in 140.15.0esr-1~deb13u1Fixed in 153.6.0esr-1~deb13u1Fixed in 153.5.1esr-1Fixed in 153.6.0esr-1
  9. 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~deb12u2Fixed in 1:140.12.0esr-1~deb13u1Fixed in 1:153.6.0esr-1~deb13u1Fixed in 1:153.5.0esr-1Fixed in 1:153.6.0esr-1
  10. Upgrade

    Upgrade Firefox to a version that resolves this vulnerability.

    Fixed in 134
  11. Upgrade

    Upgrade Thunderbird to a version that resolves this vulnerability.

    Fixed in 128.6

Event History

Jan 7, 2025
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·04:07 PM
Data Sourced
via MITRE·04:07 PM
Description
Data Sourced
via OSV·04:15 PM
DescriptionSeverityAffected Software
Data Sourced
via NVD·04:15 PM
DescriptionSeverityWeaknessAffected Software
Data Sourced
via Red Hat·05:01 PM
DescriptionSeverityAffected Software

Parent advisories

This vulnerability appears in the following advisories.

Peer vulnerabilities

Found alongside the following vulnerabilities.

Frequently Asked Questions

1

What is the severity of CVE-2025-0243?

CVE-2025-0243 is considered a critical vulnerability due to the potential for memory corruption and arbitrary code execution.

2

How do I fix CVE-2025-0243?

To fix CVE-2025-0243, update to Firefox version 134.0-1 or Thunderbird version 134, depending on the affected application.

3

Which versions of Firefox are affected by CVE-2025-0243?

CVE-2025-0243 affects Firefox versions 133 and below.

4

Which versions of Thunderbird are affected by CVE-2025-0243?

CVE-2025-0243 affects Thunderbird versions 133 and below.

5

Is there a patch available for CVE-2025-0243?

Yes, patches are available in the form of updated software versions for Firefox and Thunderbird.

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