CVE-2026-20340 Cisco Secure FMC Software - Remote Code Execution

Cisco Secure FMC Software contains an insecure deserialization vulnerability caused by unsecured deserialization of web-management user-controlled data, letting authenticated remote attackers execute arbitrary commands as root, exploit requires Security Analyst role or higher.

CVSS base score 8.8 /10
High
CISA KEV
Not listed
Public exploit
None known
Authentication
Required
EPSS
0.69% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Remote Code Execution
Impact
Remote Code Execution, Privilege Escalation
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Published
16 September 2026
Updated
15 October 2026
Weakness
CWE-502

Vendor fix

Update to the latest available version with the vulnerability fixed.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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