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Known exploited vulnerability

CVE-2026-20131

criticalCVSS 3.1 10.0In CISA KEVRansomwareEPSS 44%Published · Cisco

The short answer

CVE-2026-20131 affects Cisco Cisco Secure Firewall Management Center (FMC) and is rated critical (CVSS 10.0). CISA added it to the Known Exploited Vulnerabilities catalog on 2026-03-19: attackers are using it, so patch it first.

What it is

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.

Weakness: CWE-502.

Severity

10.0 critical

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

Exploited (CISA KEV)

Yes, since Mar 19, 2026

Federal due date Mar 22, 2026

EPSS, next 30 days

44%

Higher than 99% of scored CVEs

How it can be exploited

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Changed
Confidentiality impact
High
Integrity impact
High
Availability impact
High

What CISA says to do

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Affected products

Cisco Secure Firewall Management Center (FMC). NVD's record lists the exact affected versions.

References

Questions

Is CVE-2026-20131 being exploited?

Yes. CISA added CVE-2026-20131 to its Known Exploited Vulnerabilities catalog on 2026-03-19, with a federal remediation due date of 2026-03-22. CISA lists it as used in ransomware campaigns.

How do I fix CVE-2026-20131?

CISA's required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

From NVD, CISA KEV, FIRST EPSS and OSV.dev, checked . Status on NVD: Analyzed. The description is NVD's text, quoted as published.

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