Exploited CVEs / Cisco / CVE-2025-20333

CVE-2025-20333

Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Buffer Overflow Vulnerability. Exploitation in the wild is confirmed by CISA, not predicted. Federal agencies were required to remediate by 2025-09-26 (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.

Risk summary

CriticalCISA KEV

9.9

CVSS v3 base

71%

EPSS exploit probability

Critical

Severity

2025-09-25

Added to KEV

2025-09-26 (past due)

CISA due date

Actively exploited Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense vulnerability, Critical severity, CVSS v3 9.9. Added to the CISA KEV catalog 2025-09-25.

Senserva AI read on CVE-2025-20333 CISA required action Official fix for CVE-2025-20333 Admin questions

Senserva AI Opinion for CVE-2025-20333

The code execution half of the Cisco ASA and FTD chain: a buffer overflow in the VPN web server rated CVSS 9.9 that pairs with the CVE-2025-20362 authorization bypass for full unauthenticated device takeover. These are perimeter security appliances, so successful exploitation is a network-wide event; KEV-listed September 2025.

Do this: Patch every ASA and FTD device now and treat any that were exposed unpatched as candidates for forensic review, not just remediation.

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

Senserva AI Opinion and rich prompt for CVE-2025-20333

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

I run IT security. Facts for CVE-2025-20333, an actively exploited vulnerability (source: https://senserva.com/cve/CVE-2025-20333.html, data from CISA KEV, FIRST.org EPSS, NVD, refreshed once a day (early morning US Central)):
- CVE-2025-20333: Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Buffer Overflow Vulnerability
- Affected: Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense
- Severity: Critical, CVSS v3 9.9; EPSS 30-day exploitation probability 71%
- Added to CISA KEV: 2025-09-25; federal remediation due 2025-09-26
- Ransomware-linked: no
- CISA required action: The KEV due date refers to the deadline by which FCEB agencies are expected to review and begin implementing the guidance outlined in Emergency Directive (ED) 25-03 (URL listed below in Notes). Agencies must follow the mitigation steps provided by CISA (URL listed below in Notes) and vendor’s ins...
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.

Patch now

Exploited in the wild: confirmed by the CISA KEV catalog, not predicted.

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

Do this now: Federal remediation deadline 2025-09-26; treat it as your outer bound. Patch now and verify deployment on every exposed device.

Updated September 3, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.

Full tracking and change history for CVE-2025-20333

Published: 2025-09-25
Last revised: 2025-09-25
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 strongest signal is the Severity jump from 0.0 to 9.9 on 2026-07-17, when EPSS also entered at 40.4%. Exploit probability then climbed to 70.4% by 2026-08-24 and edged to 70.7% on 2026-08-26. The pattern shows a critical flaw with steadily rising real-world exploitation likelihood, warranting prompt patching today.

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

2025-09-25 added to the CISA KEV catalog by CISA
2026-07-17 CVSS 0.0 to 9.9; EPSS first scored at 40.4%
2026-08-24 EPSS 40.4% to 70.4%
2026-08-26 EPSS 70.4% to 70.7%

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 (BOD 22-01) remediation due date: 2025-09-26 (past due).

The KEV due date refers to the deadline by which FCEB agencies are expected to review and begin implementing the guidance outlined in Emergency Directive (ED) 25-03 (URL listed below in Notes). Agencies must follow the mitigation steps provided by CISA (URL listed below in Notes) and vendor’s instructions (URL listed below in Notes). Adhere to the applicable BOD 22-01 guidance for cloud services or discontinue use of the product if mitigations are not available.

Official fix for CVE-2025-20333

The authoritative fix and affected-version list are published by the vendor. Find the Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense advisory on Cisco Security Advisories (PSIRT).

Cisco Security Advisories (PSIRT)CISA KEV entry

Common questions about CVE-2025-20333

Is CVE-2025-20333 actively exploited?

Yes. CVE-2025-20333 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2025-09-25, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 71%.

What is the CISA deadline and required action for CVE-2025-20333?

CISA set the federal (BOD 22-01) remediation due date at 2025-09-26, which has passed; treat any unremediated system as overdue. The verbatim required action: The KEV due date refers to the deadline by which FCEB agencies are expected to review and begin implementing the guidance outlined in Emergency Directive (ED) 25-03 (URL listed below in Notes). Agencies must follow the mitigation steps provided by CISA (URL listed below in Notes) and vendor’s instructions (URL listed below in Notes). Adhere to the applicable BOD 22-01 guidance for cloud services or discontinue use of the product if mitigations are not available.

What fixes CVE-2025-20333?

The authoritative fix is in the vendor advisory: see Cisco Security Advisories (PSIRT) for the patched Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense 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-2025-20333?

Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2025-20333'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 once a day (early morning US Central).

Scope and sources

More exploited Cisco CVEs: CVE-2026-20349 CVE-2026-20316 CVE-2008-4128 CVE-2026-20230 CVE-2026-20262 CVE-2026-20245 CVE-2026-20182 CVE-2026-20133
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.