CVE-2026-20340 is a vulnerability in Cisco Secure Firewall Management Center
Published on September 16, 2026
Cisco Secure Firewall Management Center Software Deserialization Arbitrary Root Command Execution Vulnerability
A vulnerability in Cisco Secure FMC Software could allow an authenticated, remote attacker to execute arbitrary commands at the root privilege level.
This vulnerability is due to unsecured deserialization of web-management user-controlled data. An attacker could exploit this vulnerability by authenticating to the device and sending a crafted HTTP payload. A successful exploit could allow the attacker to save the crafted payload and then execute it on the underlying operating system as root.
To exploit this vulnerability, the attacker must have valid credentials for a user account with at least the role of Security Analyst (read-only).
Vulnerability Analysis
CVE-2026-20340 is exploitable with network access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to be very high.
Weakness Type
What is a Marshaling, Unmarshaling Vulnerability?
The application deserializes untrusted data without sufficiently verifying that the resulting data will be valid.
CVE-2026-20340 has been classified to as a Marshaling, Unmarshaling vulnerability or weakness.
Products Associated with CVE-2026-20340
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Affected Versions
Cisco Secure Firewall Management Center (FMC):- Version 7.0.0 is affected.
- Version 7.0.0.1 is affected.
- Version 7.0.1 is affected.
- Version 7.0.1.1 is affected.
- Version 7.0.2 is affected.
- Version 7.2.0 is affected.
- Version 7.0.2.1 is affected.
- Version 7.0.3 is affected.
- Version 7.2.0.1 is affected.
- Version 7.0.4 is affected.
- Version 7.2.1 is affected.
- Version 7.0.5 is affected.
- Version 7.3.0 is affected.
- Version 7.2.2 is affected.
- Version 7.3.1 is affected.
- Version 7.2.3 is affected.
- Version 7.2.3.1 is affected.
- Version 7.2.4 is affected.
- Version 7.0.6 is affected.
- Version 7.2.4.1 is affected.
- Version 7.2.5 is affected.
- Version 7.3.1.1 is affected.
- Version 7.4.0 is affected.
- Version 7.0.6.1 is affected.
- Version 7.2.5.1 is affected.
- Version 7.4.1 is affected.
- Version 7.2.6 is affected.
- Version 7.4.1.1 is affected.
- Version 7.0.6.2 is affected.
- Version 7.2.7 is affected.
- Version 7.2.5.2 is affected.
- Version 7.3.1.2 is affected.
- Version 7.2.8 is affected.
- Version 7.6.0 is affected.
- Version 7.4.2 is affected.
- Version 7.2.8.1 is affected.
- Version 7.0.6.3 is affected.
- Version 7.4.2.1 is affected.
- Version 7.2.9 is affected.
- Version 7.0.7 is affected.
- Version 7.7.0 is affected.
- Version 7.4.2.2 is affected.
- Version 7.2.10 is affected.
- Version 7.6.1 is affected.
- Version 7.4.2.3 is affected.
- Version 7.0.8 is affected.
- Version 7.6.2 is affected.
- Version 7.7.10 is affected.
- Version 7.2.10.1 is affected.
- Version 7.0.8.1 is affected.
- Version 7.6.2.1 is affected.
- Version 7.2.10.2 is affected.
- Version 7.7.10.1 is affected.
- Version 7.4.2.4 is affected.
- Version 7.4.3 is affected.
- Version 7.6.3 is affected.
- Version 7.7.11 is affected.
- Version 7.6.4 is affected.
- Version 10.0.0 is affected.
- Version 7.4.4 is affected.
- Version 7.4.5 is affected.
- Version 7.0.9 is affected.
- Version 7.2.11 is affected.
- Version 7.7.12 is affected.
- Version 7.6.5 is affected.
- Version 7.4.6 is affected.
- Version 10.0.1 is affected.
- Version 7.4.7 is affected.