CVE-2025-1009
Published: 04 February 2025
Summary
CVE-2025-1009 is a critical-severity Use After Free (CWE-416) vulnerability in Mozilla Firefox. Its CVSS base score is 9.8 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Drive-by Compromise (T1189); ranked in the top 25.5% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-2 (Flaw Remediation) and RA-5 (Vulnerability Monitoring and Scanning).
Deeper analysis
CVE-2025-1009 is a use-after-free vulnerability (CWE-416) triggered by crafted XSLT data that can produce a potentially exploitable crash. The flaw affects Mozilla Firefox and Thunderbird releases prior to the versions containing the fix, specifically Firefox before 135, Firefox ESR before 115.20 and 128.7, and Thunderbird before 128.7 and 135.
An unauthenticated remote attacker can supply malicious XSLT content over the network to trigger the flaw, resulting in memory corruption that may be leveraged for arbitrary code execution or denial of service, consistent with the CVSS 9.8 rating reflecting full impact on confidentiality, integrity, and availability without requiring user interaction.
Mozilla security advisories MFSA2025-07, MFSA2025-08, MFSA2025-09, and MFSA2025-10, along with the associated Bugzilla entry, document the patches that resolve the issue in the listed product versions. The associated EPSS scores remain low with only minimal movement between the recorded current and peak values.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2025-1964
Vulnerability details
An attacker could have caused a use-after-free via crafted XSLT data, leading to a potentially exploitable crash. This vulnerability was fixed in Firefox 135, Firefox ESR 115.20, Firefox ESR 128.7, Thunderbird 128.7, and Thunderbird 135.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Use-after-free in XSLT processing enables remote arbitrary code execution via malicious webpage (drive-by) or document without auth/UI, directly mapping to client-side exploitation and user execution vectors.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly mandates timely patching of known flaws like CVE-2025-1009 by upgrading to fixed Firefox and Thunderbird versions, comprehensively eliminating the use-after-free vulnerability.
Implements memory protection safeguards such as ASLR and DEP to mitigate exploitation of the use-after-free in XSLT processing, preventing arbitrary code execution despite the flaw.
Enables vulnerability scanning to identify systems with vulnerable Firefox/Thunderbird versions affected by CVE-2025-1009, supporting targeted remediation.