Is CVE-2026-20131 in the CISA KEV catalog?

Yes. CVE-2026-20131 is on the CISA Known Exploited Vulnerabilities list, added 2026-03-19, and has known ransomware campaign use.

What is the CVSS severity of CVE-2026-20131?

CVE-2026-20131 has a CVSS v3 base score of 10.0 (CRITICAL).

What is the EPSS score for CVE-2026-20131?

CVE-2026-20131 has an EPSS score of 27.55% (98th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix or mitigate CVE-2026-20131?

No published fix for CVE-2026-20131 has been found yet. It is on the CISA Known Exploited Vulnerabilities list; federal agencies must remediate by 2026-03-22. Apply the vendor's mitigations per CISA's guidance.

CVE & CISA-KEV Catalog

CVE-2026-20131

CRITICALCISA KEVEPSS 98th pctl

10.0

CVSS v3

NVD

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.

CWE-502Deserialization of Untrusted Data

How to fix

Actively exploited, no published fix found yet

Federal remediation due: 2026-03-22

Known ransomware campaign use

Mitigation guidance may be in the linked vendor advisories in the References section below.

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CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeChanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Exploit Intelligence

27.55%probability of exploitation in 30 days

98thpercentile

Very high risk: more likely to be exploited than 98% of all known CVEs.

Known Exploited Vulnerability (CISA KEV)

Remediation due: 2026-03-22

Associated with ransomware campaigns

References

Vendor Advisory1

sec.cloudapps.cisco.com

Government Resource1

cisa.gov

Technical Description1

aws.amazon.com

Related Vulnerabilities

Other CWE-502 (Deserialization of Untrusted Data) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2023-0669	High	7.2	100%	KEV + Ransom	Fix
CVE-2021-44228	Critical	10.0	100%	KEV + Ransom	Fix
CVE-2021-35464	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2023-29300	Critical	9.8	100%	KEV + Ransom	-
CVE-2025-53770	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2022-41082	High	8.0	100%	KEV + Ransom	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-03-25.