REDHAT-BUG-2517839: High severity Mozilla Firefox ESR vulnerability

Published Aug 18, 2026
·
Updated

Internally found bugs present in Firefox ESR 115.38, Firefox ESR 140.13, Firefox ESR 153.0 and Firefox 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 154, Firefox ESR 115.39, Firefox ESR 140.14, and Firefox ESR 153.1.

Affected Software

2 affected components
Mozilla Firefox ESR>=115.38<=115.38, >=140.13<=140.13, >=153.0<=153.0, >=153<=153
Mozilla Firefox>=140.13<=140.13, >=115.38<=115.38, >=153.0<=153.0, >=153<=153

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 154
  2. Upgrade

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

    Fixed in 115.39
  3. Upgrade

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

    Fixed in 140.14
  4. Upgrade

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

    Fixed in 153.1

Event History

Aug 18, 2026
Data Sourced
via Red Hat·12:52 PM
DescriptionSeverityAffected Software

Frequently Asked Questions

1

Which Firefox releases are affected, and which releases contain the fix?

The reported affected releases are Firefox ESR 115.38, Firefox ESR 140.13, Firefox ESR 153.0, and Firefox 153. The fixes are in Firefox 154, Firefox ESR 115.39, Firefox ESR 140.14, and Firefox ESR 153.1.

2

Is exploitation confirmed?

No exploitation is confirmed in the provided information. Some of the internally found bugs showed evidence of memory corruption or another security-relevant defect, and it is presumed that some could be exploitable with sufficient effort.

Contact

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