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Actively exploited

CVE-2016-9079 Mozilla Firefox, Firefox ESR, and Thunderbird Use-After-Free Vulnerability

Mozilla Firefox, Firefox ESR, and Thunderbird contain a use-after-free vulnerability in SVG Animation, targeting Firefox and Tor browser users on Windows.

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch urgentlyCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 22 Jun 2023.
  • Rated High severity (CVSS 7.5, scored by CISA).
  • It has been in the catalogue for 1,233 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

A use-after-free vulnerability in SVG Animation has been discovered. An exploit built on this vulnerability has been discovered in the wild targeting Firefox and Tor Browser users on Windows. This vulnerability affects Firefox < 50.0.2, Firefox ESR < 45.5.1, and Thunderbird < 45.5.1.

Affected Versions

ProductVersions
Mozilla Firefoxunspecified to before 50.0.2
Mozilla Firefox ESRunspecified to before 45.5.1
Mozilla Thunderbirdunspecified to before 45.5.1

From the public CVE record, as supplied by the vendor. Always confirm against the vendor advisory.

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for Mozilla Firefox, Firefox ESR, and Thunderbird. Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

    Apply updates per vendor instructions.

    Vulnerability Management
  3. 3

    Hunt for compromise

    If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.

    Incident Response
  4. 4

    Prove it is fixed

    Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.

    Penetration Testing

Vendor Advisories

Regulation

The Compliance Clock

Cyber EssentialsRated high, so if it affects devices in your Cyber Essentials scope, the update must be installed within 14 days of the vendor releasing it.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 13 Jul 2023 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

Stay Ahead

More Exploited Mozilla Flaws

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CVE-2010-3765Mozilla Multiple Products Remote Code Execution VulnerabilityAdded 6 Oct 2025CVE-2024-9680 · RansomwareMozilla Firefox Use-After-Free VulnerabilityAdded 15 Oct 2024CVE-2015-4495Mozilla Firefox Security Feature Bypass VulnerabilityAdded 25 May 2022CVE-2019-11707Mozilla Firefox and Thunderbird Type Confusion VulnerabilityAdded 23 May 2022CVE-2019-11708Mozilla Firefox and Thunderbird Sandbox Escape VulnerabilityAdded 23 May 2022CVE-2013-1690Mozilla Firefox and Thunderbird Denial-of-Service VulnerabilityAdded 28 Mar 2022

All 13 exploited Mozilla vulnerabilities

Not Sure If You Are Exposed?

Our attack surface and vulnerability teams can check your internet-facing estate for CVE-2016-9079 and every other exploited flaw on the list.

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Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2016-9079
  3. CVE record: CVE-2016-9079
  4. FIRST EPSS
  5. mozilla.org/en-US/security/advisories/mfsa2016-92/#CVE-2016-9079
  6. debian.org/security/2016/dsa-3730
  7. rhn.redhat.com/errata/RHSA-2016-2843.html
  8. security.gentoo.org/glsa/201701-35
  9. securitytracker.com/id/1037370
  10. exploit-db.com/exploits/42327/
  11. rhn.redhat.com/errata/RHSA-2016-2850.html
  12. mozilla.org/security/advisories/mfsa2016-92/