CVE-2026-74989: Internally found bugs fixed in Firefox 154

Q: Which Firefox versions are known to be affected or fixed?

Firefox 153 is affected. The issue was fixed in Firefox 154.

Q: Is exploitation known to be practical?

The affected bugs were internally found and showed evidence of memory corruption or another security-relevant defect. Mozilla states that some could potentially have been exploited with enough effort, but the available information does not specify attacker prerequisites or a confirmed exploitation method.

Published Aug 18, 2026

Updated

Internally found bugs present in 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.

Affected Software

2 affected componentsFixes available

Firefox=153, =154

Mozilla Firefox<154

154

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 154
Upgrade
Upgrade Firefox to a version that resolves this vulnerability.
Fixed in 154

Event History

Aug 18, 2026

CVE Published

via Mozilla·12:00 AM

Data Sourced

via Mozilla·12:00 AM

DescriptionSeverityAffected Software

CVE Published

via MITRE·12:23 PM

Data Sourced

via MITRE·12:23 PM

Description

Parent advisories

This vulnerability appears in the following advisories.

MFSA2026-74

Peer vulnerabilities

Found alongside the following vulnerabilities.

Frequently Asked Questions

Which Firefox versions are known to be affected or fixed?