CVE-2025-20333
Memory Safety in Cisco Adaptive Security Appliance Software 9.12 – 9.12.4.72
Raw vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:HSummary
CVE-2025-20333 is a critical-severity Classic Buffer Overflow (CWE-120) vulnerability in Cisco Adaptive Security Appliance Software. Its CVSS base score is 9.9 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked in the top 1% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-10 (Information Input Validation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
A vulnerability in the VPN web server of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software stems from improper validation of user-supplied input in HTTP(S) requests. Tracked as CVE-2025-20333 with a CVSS score of 9.9 and associated with CWE-120, the flaw permits an authenticated remote attacker to send specially crafted requests that result in arbitrary code execution as root on affected devices.
An attacker in possession of valid VPN user credentials can exploit the issue over the network without user interaction to achieve complete compromise of the target appliance. Successful exploitation grants full control of the device, including the ability to execute arbitrary code with the highest privileges.
Cisco has published an advisory detailing the affected versions along with remediation guidance, and the vulnerability appears in CISA's Known Exploited Vulnerabilities catalog, confirming active exploitation in the wild. The associated EPSS score rose from a low baseline to a peak of 0.4143 before settling at a current value of 0.2655, indicating that exploitation interest increased after public disclosure.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2025-31140
Vulnerability Data
A vulnerability in the VPN web server of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an authenticated, remote attacker to execute arbitrary code on an affected device. This vulnerability…
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is due to improper validation of user-supplied input in HTTP(S) requests. An attacker with valid VPN user credentials could exploit this vulnerability by sending crafted HTTP requests to an affected device. A successful exploit could allow the attacker to execute arbitrary code as root, possibly resulting in the complete compromise of the affected device.
- CWE(s)
- KEV Date Added
- 25 September 2025
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V5.2.1
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and analysis can find missing size checks before deployment.
Input validation directly enforces size checks before buffer copies.
Engineering principles require bounds checking and safe buffer handling in design.
Memory protection limits the impact of an overflow once it occurs.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure development practices directly enforce bounds checking and input validation that prevent classic buffer overflows.
Vulnerability identification processes such as code review or scanning detect classic buffer overflows before exploitation.
Routine patching replaces vulnerable code containing unchecked buffer copies with corrected versions.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Secure coding directly requires bounds-checked memory operations, addressing the root cause of CWE-120.
Security testing in development and acceptance can detect buffer overflows through fuzzing and static analysis, though it does not prevent them at the source.
Secure development life cycle mandates processes that can include input validation and bounds checking to prevent buffer overflows.
Application security requirements can specify input-size validation and safe buffer handling to mitigate classic buffer overflows.
Secure system architecture and engineering principles promote defensive coding patterns that reduce the likelihood of unchecked buffer copies.