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CVE-2026-109773 Mozilla CVE debrief

Mozilla Firefox vulnerability CVE-2026-109773 causes denial-of-service in the Sync component. This issue was addressed in Firefox 158. The vulnerability affects the Sync component of Mozilla Firefox, potentially allowing attackers to cause a denial-of-service condition. Defenders should assess exposure and verify the need for updates to Firefox 158. The CVE record and source item provide limited information about the vulnerability, and defenders may need to review additional sources for more context.

Vendor
Mozilla
Product
Firefox
CVSS
Unknown
CISA KEV
Not listed in stored evidence
Original CVE published
2026-10-13
Original CVE updated
2026-10-13
Advisory published
2026-10-13
Advisory updated
2026-10-13

Who should care

Defenders responsible for managing Mozilla Firefox deployments should assess exposure and verify the need for updates to Firefox 158. This includes operators, platform administrators, vulnerability management teams, and security teams who need to prioritize verifying exposure in their Firefox deployments and assess the need for updates.

Why it matters

CVE-2026-109773 is a denial-of-service vulnerability in the Sync component of Mozilla Firefox. Defenders should prioritize verifying exposure in their Firefox deployments and assess the need for updates to Firefox 158.

  • Verify exposure in Firefox deployments
  • Assess the need for updates to Firefox 158

Technical summary

CVE-2026-109773 is a denial-of-service vulnerability in the Sync component of Mozilla Firefox. The issue was fixed in Firefox 158. The vulnerability affects the Sync component of Mozilla Firefox, potentially allowing attackers to cause a denial-of-service condition. Defenders should prioritize verifying exposure in their Firefox deployments and assess the need for updates.

Defensive priority

Defenders should prioritize verifying exposure in their Firefox deployments and assess the need for updates.

Recommended defensive actions

  • Verify Firefox version and update to 158 if necessary
  • Review Mozilla security advisory for additional information
  • Assess exposure in Firefox deployments
  • Verify exposure in managed environments and assign an owner for follow-up
  • Review compensating controls for exposed systems while remediation is scheduled and verified

Evidence notes

The CVE record and source item provide limited information about the vulnerability. The Mozilla security advisory (MFSA 2026-106) may offer additional context. Defenders should verify exposure in their Firefox deployments and assess the need for updates to Firefox 158. The vulnerability was fixed in Firefox 158, and defenders should review the Mozilla security advisory for more information.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-109773 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-109773

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-109773 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-109773

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Denial-of-service in the Sync component

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/109xxx/CVE-2026-109773.json

    cve_program_cvelist_v5

  • Source reference

    Unverified legacy reference

    URL: https://www.mozilla.org/security/advisories/mfsa2026-106/

    Supplemental source

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.