CVE-2026-6785: Memory safety bugs fixed in Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird ESR 140.10, Firefox 150 and Thunderbird 150

Published Apr 21, 2026
·
Updated

Memory safety bugs present in Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird ESR 140.9, Firefox 149 and Thunderbird 149. 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.

Affected Software

9 affected componentsFixes available
Mozilla Firefox ESR<115.35
115.35
Mozilla Firefox ESR<140.10
140.10
Mozilla Firefox<150
150
Mozilla Thunderbird<150
150
Mozilla Thunderbird<140.10
140.10
Mozilla Firefox<115.35.0
Mozilla Firefox<150.0
Mozilla Firefox>=140.0<140.10.0
Mozilla Thunderbird>=140.0<140.10.0

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 115.35
  2. Upgrade

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

    Fixed in 140.10
  3. Upgrade

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

    Fixed in 150
  4. Upgrade

    Upgrade Mozilla Firefox ESR to a version that resolves this vulnerability.

    Fixed in 115.35
  5. Upgrade

    Upgrade Mozilla Firefox ESR to a version that resolves this vulnerability.

    Fixed in 140.10
  6. Upgrade

    Upgrade Mozilla Firefox to a version that resolves this vulnerability.

    Fixed in 150
  7. Upgrade

    Upgrade Mozilla Thunderbird ESR to a version that resolves this vulnerability.

    Fixed in 140.10
  8. Upgrade

    Upgrade Mozilla Thunderbird to a version that resolves this vulnerability.

    Fixed in 150

Event History

Apr 21, 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·12:41 PM
Data Sourced
via MITRE·12:41 PM
Description
Data Sourced
via Red Hat·02:03 PM
DescriptionSeverityAffected Software
Apr 26, 2026
Data Sourced
via NVD·07:53 PM
DescriptionSeverityWeaknessAffected Software
Jan 24, 58373
Event
via NVD·04:46 AM

Parent advisories

This vulnerability appears in the following advisories.

Peer vulnerabilities

Found alongside the following vulnerabilities.

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Frequently Asked Questions

1

What is the severity of CVE-2026-6785?

The severity of CVE-2026-6785 is rated as moderate due to memory safety issues impacting multiple versions of Firefox and Thunderbird.

2

How do I fix CVE-2026-6785?

To fix CVE-2026-6785, upgrade to Firefox ESR 115.35, Firefox ESR 140.10, or Thunderbird 150.

3

What versions of Firefox are affected by CVE-2026-6785?

CVE-2026-6785 affects Firefox versions 115.34, 140.9, and 149.

4

What versions of Thunderbird are affected by CVE-2026-6785?

CVE-2026-6785 affects Thunderbird versions 140.9 and 149.

5

What type of vulnerabilities does CVE-2026-6785 address?

CVE-2026-6785 addresses memory safety vulnerabilities that can lead to memory corruption.

Company

Resources

Contact

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