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CVE-2026-20131

CRITICALCVSS 10/10Actively ExploitedEPSS 27.55%

Last modified

CVE-2026-20131 is a critical-severity vulnerability rated 10/10 on the CVSS scale. A vulnerability in the web-based management interface of Cisco Secure Firewall Management Center (FMC) Software could allow an unauthenticated, remote attacker to execute arbitrary Java code as root on an affected device. This vulnerability is due to insecure deserialization of a user-supplied Java byte stream. An attacker could exploit this vulnerability by sending a crafted serialized Java object to the web-based management interface of an affected device. CISA has confirmed active exploitation in the wild. EPSS estimates a 27.55% chance of exploitation in the next 30 days.

Description

A vulnerability in the web-based management interface of Cisco Secure Firewall Management Center (FMC) Software could allow an unauthenticated, remote attacker to execute arbitrary Java code as root on an affected device. This vulnerability is due to insecure deserialization of a user-supplied Java byte stream. An attacker could exploit this vulnerability by sending a crafted serialized Java object to the web-based management interface of an affected device. A successful exploit could allow the attacker to execute arbitrary code on the device and elevate privileges to root. Note: If the FMC management interface does not have public internet access, the attack surface that is associated with this vulnerability is reduced.

Metrics

CVSS 3.1
10/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

EPSS Probability
27.55%

97.8th percentile

Probability of exploitation in the next 30 days. Learn more

Exploitation Status

This vulnerability is listed in CISA’s Known Exploited Vulnerabilities catalog, confirming active exploitation in the wild. Federal agencies must remediate by .

Weakness Enumeration

Affected Software

VendorProductVersions
CiscoSecure Firewall Management Center6.4.0.13
CiscoSecure Firewall Management Center6.4.0.14
CiscoSecure Firewall Management Center6.4.0.15
CiscoSecure Firewall Management Center6.4.0.16
CiscoSecure Firewall Management Center6.4.0.17
CiscoSecure Firewall Management Center6.4.0.18
CiscoSecure Firewall Management Center7.0.0
CiscoSecure Firewall Management Center7.0.0.1
CiscoSecure Firewall Management Center7.0.1
CiscoSecure Firewall Management Center7.0.1.1
CiscoSecure Firewall Management Center7.0.2
CiscoSecure Firewall Management Center7.0.2.1
CiscoSecure Firewall Management Center7.0.3
CiscoSecure Firewall Management Center7.0.4
CiscoSecure Firewall Management Center7.0.5
CiscoSecure Firewall Management Center7.0.6
CiscoSecure Firewall Management Center7.0.6.1
CiscoSecure Firewall Management Center7.0.6.2
CiscoSecure Firewall Management Center7.0.6.3
CiscoSecure Firewall Management Center7.0.7
CiscoSecure Firewall Management Center7.0.8
CiscoSecure Firewall Management Center7.0.8.1
CiscoSecure Firewall Management Center7.1.0
CiscoSecure Firewall Management Center7.1.0.1
CiscoSecure Firewall Management Center7.1.0.2
CiscoSecure Firewall Management Center7.1.0.3
CiscoSecure Firewall Management Center7.2.0
CiscoSecure Firewall Management Center7.2.0.1
CiscoSecure Firewall Management Center7.2.1
CiscoSecure Firewall Management Center7.2.2
CiscoSecure Firewall Management Center7.2.3
CiscoSecure Firewall Management Center7.2.3.1
CiscoSecure Firewall Management Center7.2.4
CiscoSecure Firewall Management Center7.2.4.1
CiscoSecure Firewall Management Center7.2.5
CiscoSecure Firewall Management Center7.2.5.1
CiscoSecure Firewall Management Center7.2.5.2
CiscoSecure Firewall Management Center7.2.6
CiscoSecure Firewall Management Center7.2.7
CiscoSecure Firewall Management Center7.2.8
CiscoSecure Firewall Management Center7.2.8.1
CiscoSecure Firewall Management Center7.2.9
CiscoSecure Firewall Management Center7.2.10
CiscoSecure Firewall Management Center7.2.10.1
CiscoSecure Firewall Management Center7.2.10.2
CiscoSecure Firewall Management Center7.3.0
CiscoSecure Firewall Management Center7.3.1
CiscoSecure Firewall Management Center7.3.1.1
CiscoSecure Firewall Management Center7.3.1.2
CiscoSecure Firewall Management Center7.4.0

Showing 50 of 71 affected configurations. See NVD for the full list.

References

Timeline

Published
Last Modified
Status
Analyzed

Frequently Asked Questions

What is CVE-2026-20131?
A vulnerability in the web-based management interface of Cisco Secure Firewall Management Center (FMC) Software could allow an unauthenticated, remote attacker to execute arbitrary Java code as root on an affected device. This vulnerability is due to insecure deserialization of a user-supplied Java byte stream. An attacker could exploit this vulnerability by sending a crafted serialized Java object to the web-based management interface of an affected device. A successful exploit could allow the attacker to execute arbitrary code on the device and elevate privileges to root. Note: If the FMC management interface does not have public internet access, the attack surface that is associated with this vulnerability is reduced.
How severe is CVE-2026-20131?
CVE-2026-20131 has a CVSS score of 10/10 (CRITICAL severity). The EPSS model estimates a 27.55% probability of exploitation in the next 30 days. This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog.
How do I fix CVE-2026-20131?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-20131?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST