9.8

CVE-2026-20242: cisco cisco secure firewall management center (fmc) Deserialization of Untrusted Data

CVSS: 9.8v3.1CriticalAwaiting analysis
Published 16-09-2026Last modified 18-09-2026
Open JSON

Vulnerability summary

CVE-2026-20242 is a critical (CVSS 9.8) Deserialization of Untrusted Data vulnerability in cisco cisco secure firewall management center (fmc). EPSS estimates a 0.64% chance of exploitation in the next 30 days, higher than 49.7% of scored vulnerabilities.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.8/10
010
Critical · v3.1 (CVE.org)
EPSS score
0.64%
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 the External Database Access feature of Cisco Secure Firewall Management Center (FMC) Software could allow an unauthenticated, remote attacker to execute arbitrary commands as root on an affected device. This vulnerability is due to insecure deserialization of a user-supplied Java byte stream from a host that is configured in the external database access list. An attacker could exploit this vulnerability by sending a crafted, serialized Java byte stream to a specific TCP port of an affected device. A successful exploit could allow the attacker to execute arbitrary commands on the device and elevate privileges to root. Notes: This vulnerability can be exploited only by an attacker who has control of a host in the external database access list. If the FMC management interface does not have public internet access, the attack surface that is associated with this vulnerability is reduced.

CVSS metrics

2 scores · 2 sources · 1 version

EPSS trend

Probability

0.64%

Chance of exploitation in the next 30 days

Percentile

50%

Versus all other CVEs

30-day change

0.00 pp

From 0.64% on 20-09-2026

20-09-202620-10-2026
EPSS score
0.64%

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