CVE-2026-109752 Mozilla CVE debrief

Who should care

Defenders responsible for managing Mozilla Firefox deployments should assess exposure and apply patches as necessary. This includes verifying Firefox version, reviewing and updating inventory of Firefox deployments, and monitoring for potential exploitation attempts. Additionally, defenders should prioritize verifying exposure in their Firefox deployments and applying the available patches to prevent potential exploitation.

Why it matters

CVE-2026-109752 is a use-after-free vulnerability in the DOM: Workers component of Mozilla Firefox. Defenders should prioritize verifying exposure in their Firefox deployments and applying the available patches.

• Verify exposure in Firefox deployments
• Apply patches to prevent potential exploitation
• Monitor for potential exploitation attempts

Technical summary

The CVE record describes a use-after-free vulnerability in the DOM: Workers component of Mozilla Firefox. The vulnerability was fixed in Firefox 158 and Firefox ESR 153.5. This vulnerability affects the DOM: Workers component of Mozilla Firefox, potentially impacting user data and system stability. The technical details of the vulnerability are not publicly available, but defenders should prioritize verifying exposure in their Firefox deployments and applying the available patches to prevent potential exploitation.

Defensive priority

Defenders should prioritize verifying exposure in their Firefox deployments and applying the available patches.

Recommended defensive actions

• Verify Firefox version and apply patches if necessary
• Review and update inventory of Firefox deployments
• Monitor for potential exploitation attempts
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed

Evidence notes

The CVE record and source item provide limited information about the vulnerability. The Mozilla security advisories (MFSA 2026-106 and MFSA 2026-108) may contain additional details. However, due to limited source detail, defenders should verify exposure in their Firefox deployments and apply patches as necessary. Additional verification tasks include reviewing inventory of Firefox deployments and monitoring for potential exploitation attempts. The CVE record does not provide explicit evidence of exploitation or affected scope.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.