Cisco Secure Firewall Management Center Software Deserialization Arbitrary Root Command Execution Vulnerability

published 2026-09-16 53 d ago modified 2026-09-18 51 d ago also EUVD-2026-81116

cvss: 8.8; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.7%; EPSS 0.7% chance of exploitation in 30 days, percentile 55%
public exploits: 0; none known

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).

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: total
Assessed: 53 d ago (2026-09-17)

Exploit prediction

0.74% chance of exploitation in the next 30 days, higher than 55% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	8.8	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

Cisco Cisco Secure Firewall Management Center (FMC)

Classification

Weakness

CWE-502 Deserialization of Untrusted Data

References

sec.cloudapps.cisco.com /security/center/content/CiscoSecurityAdvisory/cisco-sa-fmc-mulivulns-4PsnFwvx

Sources

CVE List CVE-2026-20340
NVD CVE-2026-20340

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Summary