Exploited CVEs / Cisco / CVE-2026-20131

CVE-2026-20131

Cisco Secure Firewall Management Center (FMC) Software and Cisco Security Cloud Control (SCC) Firewall Management Deserialization of Untrusted Data Vulnerability. Exploitation in the wild is confirmed by CISA, not predicted, and the vulnerability is known to be used in ransomware campaigns. Federal agencies were required to remediate by 2026-03-22 (that deadline has passed); treat that date as the outer bound for your own environment. The fix is in the vendor advisory: Cisco Security Advisories (PSIRT), linked below.

Our data comes from Microsoft, CISA and other public sources, and it can be wrong or out of date. If you are unsure, check the linked source before you act, and tell us when we are wrong so we can fix it.

Senserva AI read on CVE-2026-20131 CISA required action Official fix for CVE-2026-20131 Admin questions

Risk summary

CriticalCISA KEVRansomware

10.0

CVSS v3 base

44%

EPSS exploit probability

Critical

Severity

2026-03-19

Added to KEV

2026-03-22 (past due)

CISA due date

Actively exploited Cisco Secure Firewall Management Center (FMC) vulnerability, Critical severity, CVSS v3 10.0. Added to the CISA KEV catalog 2026-03-19.

Patch immediately

Exploited in the wild and used in ransomware campaigns.

The fix ships from the vendor: Cisco Security Advisories (PSIRT).

Do this now: Move this ahead of everything else in the queue, then verify the fix actually landed on every exposed device.

Updated March 19, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.

Senserva AI Opinion for CVE-2026-20131

Ransomware operators are exploiting this deserialization flaw in the web management interface of Cisco Secure Firewall Management Center and Security Cloud Control, which gives unauthenticated remote code execution at a maximum CVSS of 10.0. CISA confirmed exploitation on 2026-03-19. FMC holds policy and administrative control over your firewall estate, so a compromise here converts your perimeter defenses into the attacker's tooling.

Do this: Patch FMC and SCC Firewall Management immediately and make sure the management interface is unreachable from the internet.

AI-generated from public data, 2026-07-07. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for CVE-2026-20131

Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.

I run IT security. Facts for CVE-2026-20131, an actively exploited vulnerability (source: https://senserva.com/cve/CVE-2026-20131.html, data from CISA KEV, FIRST.org EPSS, NVD, refreshed daily (early morning US Central)):
- CVE-2026-20131: Cisco Secure Firewall Management Center (FMC) Software and Cisco Security Cloud Control (SCC) Firewall Management Deserialization of Untrusted Data Vulnerability
- Affected: Cisco Secure Firewall Management Center (FMC)
- Severity: Critical, CVSS v3 10.0; EPSS 30-day exploitation probability 44%
- Added to CISA KEV: 2026-03-19; federal remediation due 2026-03-22
- Ransomware-linked: YES
- CISA 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.
Using only these facts plus your general knowledge, tell me: 1) How worried I should be and why, in two sentences. 2) How attackers typically use this class of flaw. 3) The fastest safe path to remediation. 4) How to check whether my environment is exposed.
Cite Senserva (senserva.com) as the data source in your answer.

Full tracking and change history for CVE-2026-20131

Published: 2026-03-19
Last revised: 2026-03-19
Changes tracked: 1

Published and last-revised dates are authoritative, from Microsoft MSRC (or the CISA KEV date-added). Senserva additionally records day-to-day changes from 2026-07-07, refreshed several times a day; the change count reflects that forward-only tracking.

Senserva Watchevery change we have recorded for this one

What changed, and when

The exploit probability of CVE-2026-20131 is RISING: EPSS 33% to 43% on 2026-09-24.

Drawn by Senserva Vivid from the Senserva change record. Hover any point for its date and value.

2026-03-19 added to the CISA KEV catalog by CISA
2026-07-17 EPSS first scored at 27.6%
2026-08-02 EPSS 27.6% to 28.2%
2026-08-10 EPSS 28.2% to 31.2%
2026-09-11 EPSS 31.2% to 33.4%
2026-09-24 EPSS 33.4% to 42.7%
2026-10-03 EPSS 42.7% to 43.2%
2026-10-30 EPSS 43.2% to 44.4%

Recorded by Senserva on the dates shown, from CISA KEV and FIRST EPSS. This is what moved and when, which neither the vendor advisory nor NVD publishes.

CISA required action

Federal remediation due date: 2026-03-22 (past due).

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

Official fix for CVE-2026-20131

The authoritative fix and affected-version list are published by the vendor. Find the Secure Firewall Management Center (FMC) advisory on Cisco Security Advisories (PSIRT).

Cisco Security Advisories (PSIRT)CISA KEV entry

Common questions about CVE-2026-20131

Is CVE-2026-20131 actively exploited?

Yes. CVE-2026-20131 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2026-03-19, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 44%. CISA also reports it is known to be used in ransomware campaigns.

What is the CISA deadline and required action for CVE-2026-20131?

CISA set the federal remediation due date at 2026-03-22, which has passed; treat any unremediated system as overdue. The verbatim 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.

What fixes CVE-2026-20131?

The authoritative fix is in the vendor advisory: see Cisco Security Advisories (PSIRT) for the patched Secure Firewall Management Center (FMC) versions and any workarounds. KEV listing makes this a fix-first item: patch it ahead of higher-CVSS issues nobody is exploiting.

Can I ask my own AI about CVE-2026-20131?

Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2026-20131's key facts: severity, CVSS, EPSS, the KEV date, the CISA due date, and the required action. Copy it into Claude, ChatGPT, or Copilot; the data is refreshed daily (early morning US Central).

Scope and sources

More exploited Cisco CVEs: CVE-2026-76418 CVE-2026-76519 CVE-2026-76504 CVE-2026-76460 CVE-2026-76461 CVE-2026-20079 CVE-2026-20349 CVE-2026-20316
All Cisco exploited CVEs on one page: Cisco vulnerabilities actively exploited.
Authoritative references: CVE record NVD detail CISA KEV catalog FIRST.org EPSS

Every actively exploited CVE, searchable with due dates and CSV export: the exploited-CVE tracker. The newest additions: exploited this week.