Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Buffer Overflow Vulnerability
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…
Severity = CVSS. Probability = EPSS (FIRST). Exploitation = public signals: KEV, EUVD, ransomware, EPSS above 10 %, no account required.
Exploitation probability EPSS · FIRST
Exploitation signals 3 / 5
- KEV catalog (CISA)25 Sept 2025
- Exploited in EUVD (ENISA)25 Sept 2025
- Used by ransomwareno
- EPSS above 10 %71.2%
- No account, over the networkno
What to do
Fix
Apply the vendor’s fix as soon as it is available.
CISA guidance: The KEV due date refers to the deadline by which FCEB agencies are expected to review and begin implementing the guidance outlined in Emergency Directive (ED) 25-03 (URL listed below in Notes). Agencies must follow the mitigation steps provided by CISA (URL listed below in Notes) and vendor’s instructions (URL listed below in Notes). Adhere to the applicable BOD 22-01 guidance for cloud services or discontinue use of the product if mitigations are not available.
Meanwhile
Take the service off the internet or restrict access to it, watch the logs and look for signs of compromise.
Manufacturers (CRA)
Exploited vulnerability in your product: early warning to ENISA within 24 h, then notification within 72 h (Article 14 of the Cyber Resilience Act). The CRA explained
Description ENISA EUVD
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 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.
Affected products
- 9.18.1
- 9.8.4.46
- 9.8.4.8
- 9.12.4.29
- 9.19.1.27
- 9.16.3.23
- 9.17.1.11
- 9.22.1.1
- 6.6.5.1
- 9.8.2.28
- 9.16.4
- 9.8.2.26
Open source packages OSV
Affected libraries according to OSV, with fixed versions.
Timeline
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Published
-
Exploitation reported (ENISA)
-
Added to the KEV catalog
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CISA remediation due date
-
EPSS peak: 71.2%
References
Other exploited vulnerabilities from the same vendor
- CVE-2026-76418Cisco Secure Firewall ASA Software and Cisco Secure FTD Software Unchecked Return Value to NULL Pointer Dereference Vulnerability5.3 · Rising fast
- CVE-2026-76519Cisco Secure Email Gateway Relative Path Traversal Vulnerability5.8 · Rising fast
- CVE-2026-76504Cisco Catalyst SD-WAN Manager Hex Encoding Vulnerability7.5 · Actively exploited
- CVE-2026-76460Cisco Identity Services Engine Incorrect Use of Privileged APIs Vulnerability8.7 · Actively exploited
- CVE-2026-76461Cisco Secure Email Gateway SQL Injection Vulnerability7.2 · Actively exploited
- CVE-2026-20079Cisco Firewall Management Center Authentication Bypass Using an Alternate Path or Channel Vulnerability9.1 · Actively exploited