CVE-2026-20341 Cisco Secure FMC Software - Authentication Bypass

Cisco Secure FMC Software contains an insecure deserialization vulnerability in the sftunnel inter-device communication protocol, letting authenticated remote attackers gain root privileges by sending crafted RPCs, exploit requires valid administrative credentials.

CVSS base score 9.1 /10
Critical
CISA KEV
Not listed
Public exploit
None known
Authentication
Required
EPSS
0.45% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Authentication Bypass
Impact
Privilege Escalation
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/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 of Cisco Secure FMC Software.

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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