CVE-2026-109745 Mozilla CVE debrief

Who should care

Defenders responsible for Firefox deployments, especially those using versions prior to 158 or Firefox ESR versions prior to 153.5, should assess exposure and prioritize remediation.

Why it matters

CVE-2026-109745 is a sandbox escape vulnerability in Mozilla Firefox due to uninitialized memory in the DOM: Web Serial component. Defenders should verify exposure, especially in Firefox versions prior to 158 or Firefox ESR versions prior to 153.5, and prioritize remediation. Specific details about exploitation or victim data are not provided, requiring verification from official sources.

• Potential sandbox escape in Firefox deployments
• Need to verify exposure in Firefox versions prior to 158 or Firefox ESR versions prior to 153.5
• Remediation priority for affected Firefox versions

Technical summary

The vulnerability CVE-2026-109745 in Mozilla Firefox allows for a sandbox escape due to uninitialized memory in the DOM: Web Serial component. It was fixed in Firefox 158 and Firefox ESR 153.5. This issue impacts Firefox deployments, particularly those using versions prior to 158 or Firefox ESR versions prior to 153.5. Defenders should assess exposure and prioritize remediation based on official advisories and CVE details. The vulnerability's technical framing involves uninitialized memory in the DOM: Web Serial component, which could lead to sandbox escape if exploited.

Defensive priority

Defenders should prioritize verifying exposure in Firefox deployments, especially those using versions prior to 158 or Firefox ESR versions prior to 153.5, and ensure timely remediation.

Recommended defensive actions

• Verify Firefox version and update to 158 or Firefox ESR 153.5 if necessary
• Review and implement security advisories from Mozilla
• Monitor for potential exploitation attempts
• Conduct exposure review for Firefox deployments
• Check asset inventory for affected versions
• Implement compensating controls for exposed systems
• Track exceptions and retest remediated assets

Evidence notes

The CVE record and source item provide details on the vulnerability, its impact, and fixed versions. However, specific details about exploitation or victim data are not provided. Defenders should verify exposure in Firefox deployments, especially those using versions prior to 158 or Firefox ESR versions prior to 153.5, and prioritize remediation based on official advisories. The CVE Program record (CVE-2026-109745) and NIST NVD vulnerability detail offer additional context for assessing affected scope and vendor guidance.

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.