8.8

CVE-2026-20340: cisco cisco secure firewall management center (fmc) Deserialization of Untrusted Data

CVSS: 8.8v3.1HighAwaiting analysis
Published 16-09-2026Last modified 18-09-2026
Open JSON

Vulnerability summary

CVE-2026-20340 is a high (CVSS 8.8) Deserialization of Untrusted Data vulnerability in cisco cisco secure firewall management center (fmc). EPSS estimates a 0.69% chance of exploitation in the next 30 days, higher than 52% of scored vulnerabilities.

Overall risk
35/100
0100
Medium · default modelHow is this calculated?
CVSS score
8.8/10
010
High · v3.1 (CVE.org)
EPSS score
0.69%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 16-09-2026
    PublishedVulnerability first disclosed.
  2. 18-09-2026
    Last modifiedVulnerability information updated.

Description

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).

CVSS metrics

2 scores · 2 sources · 1 version

EPSS trend

Probability

0.69%

Chance of exploitation in the next 30 days

Percentile

52%

Versus all other CVEs

30-day change

0.00 pp

From 0.69% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.69%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Cisco1 product
  • cisco secure firewall management center (fmc)7.0.0 | 7.0.0.1 | 7.0.1 | 7.0.1.1 | 7.0.2 | 7.2.0 | 7.0.2.1 | 7.0.3 | 7.2.0.1 | 7.0.4 | 7.2.1 | 7.0.5 | 7.3.0 | 7.2.2 | 7.3.1 | 7.2.3 | 7.2.3.1 | 7.2.4 | 7.0.6 | 7.2.4.1 | 7.2.5 | 7.3.1.1 | 7.4.0 | 7.0.6.1 | 7.2.5.1 | 7.4.1 | 7.2.6 | 7.4.1.1 | 7.0.6.2 | 7.2.7 | 7.2.5.2 | 7.3.1.2 | 7.2.8 | 7.6.0 | 7.4.2 | 7.2.8.1 | 7.0.6.3 | 7.4.2.1 | 7.2.9 | 7.0.7 | 7.7.0 | 7.4.2.2 | 7.2.10 | 7.6.1 | 7.4.2.3 | 7.0.8 | 7.6.2 | 7.7.10 | 7.2.10.1 | 7.0.8.1 | 7.6.2.1 | 7.2.10.2 | 7.7.10.1 | 7.4.2.4 | 7.4.3 | 7.6.3 | 7.7.11 | 7.6.4 | 10.0.0 | 7.4.4 | 7.4.5 | 7.0.9 | 7.2.11 | 7.7.12 | 7.6.5 | 7.4.6 | 10.0.1 | 7.4.7

1 vendor · 1 product

References

1 links