What is the CVSS score of CVE-2025-20333?

CVE-2025-20333 has a CVSS 3.1 base score of 9.9 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H. EPSS exploitation probability: 18.8%.

Is CVE-2025-20333 being actively exploited?

Yes, CVE-2025-20333 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, confirming active in-the-wild exploitation. Immediate patching is required.

How to fix or mitigate CVE-2025-20333?

Within 24 hours: Identify all affected systems and apply vendor patches immediately. If patching is delayed, consider network segmentation to limit exposure.

Adaptive Security Appliance Software CVE-2025-20333

CRITICAL

Classic Buffer Overflow (CWE-120)

2025-09-25 psirt@cisco.com

RCE Buffer Overflow Cisco Adaptive Security Appliance Software Firepower Threat Defense

9.9

CVSS 3.1 · Vendor: cisco

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Vulnerability Assessment

Weakness	CWE CWE-120 OWASP Top 10:2025 A06:2021 - Vulnerable and Outdated Components ASVS 5.0 V15 - Secure Coding and Architecture Buffer copy size validation MITRE ATT&CK 1 technique across 1 tactic: Execution The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Impact	CVSS score of 9.9 (CRITICAL). Attack characteristics: network attack vector, low complexity, low privileges required, no user interaction not required. CISA has confirmed active exploitation in the wild. EPSS exploitation probability: 18.76%.
Exploit ScenarioDerived	A remote attacker could overflow a buffer to corrupt adjacent memory by sending crafted requests to the affected application.

Emergency Immediate action required. Why: CRITICAL + in CISA KEV (actively exploited), no patch available.

Exploited in the wild (CISA KEV) No patch listed yet 18.8% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 28, 2026

A vulnerability in the VPN web server of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an authenticated, remote. Rated critical severity (CVSS 9.9), this vulnerability is remotely exploitable, low attack complexity. Actively exploited in the wild (cisa kev) and EPSS exploitation probability 18.8%.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Always validate buffer sizes before copy operations. Use bounded functions (strncpy, snprintf). Enable compiler protections.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified as Buffer Copy without Size Check (CWE-120), which allows attackers to overflow a buffer to corrupt adjacent memory. A vulnerability in the VPN web server of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an authenticated, remote attacker to execute arbitrary code on an affected device. This vulnerability is due to improper validation of user-supplied input in HTTP(S) requests. An attacker with valid VPN user credentials could exploit this vulnerability by sending crafted HTTP requests to an affected device. A successful exploit could allow the attacker to execute arbitrary code as root, possibly resulting in the complete compromise of the affected device. Affected products include: Cisco Adaptive Security Appliance Software, Cisco Firepower Threat Defense.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (cisco) PRIMARY 9.9 CRITICAL

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

Primary rating from Vendor (cisco) · only source for this CVE.

CVSS VectorVendor: cisco

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Changed

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Added to CISA KEV

Oct 28, 2025 - 13:58 cisa

CISA KEV

CVE Published

Sep 25, 2025 - 16:15 nvd

CRITICAL 9.9

DescriptionCVE.org

A vulnerability in the VPN web server of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an authenticated, remote attacker to execute arbitrary code on an affected device. This vulnerability is due to improper validation of user-supplied input in HTTP(S) requests. An attacker with valid VPN user credentials could exploit this vulnerability by sending crafted HTTP requests to an affected device. A successful exploit could allow the attacker to execute arbitrary code as root, possibly resulting in the complete compromise of the affected device.

Executive ViewAI

Why It Matters

CVE-2025-20333 presents critical security risk, a buffer overflow vulnerability rated CVSS 9.9. Exploitation could allow attackers to corrupt memory, crash the application, or potentially execute arbitrary code. This vulnerability is actively exploited in the wild (KEV-listed) and requires immediate remediation. Immediate patching is required per CISA KEV mandate.

Business Impact: Severe

Compensating Controls

Apply vendor patch. If immediate patching is not feasible: (1) Enable ASLR and DEP where available; (2) Implement network segmentation; (3) Monitor for exploitation indicators.

Threat Intelligence Overview

Threat Score

6.0/10

Composite threat intelligence

EPSS Score

18.8%

Top 5% exploitable

Threat Intel

1 sources

Data Quality

5 sources

Confidence: Medium

NVD

CVE.org

CISA KEV

EPSS CISA CERT-EU

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity CRITICAL

CISA KEV Yes

Public POC No

EPSS 18.8%

Patch available No

Active threat Yes

Deciding rule

CRITICAL + in CISA KEV (actively exploited), no patch available

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Immediate

Exploitation· derived

Active

System Exposure· derived

Open

Automatable· derived

Human Impact

Very High

Priority Score

129

Low Medium High Critical

KEV: +50

EPSS: +19

CVSS: +50

PoC: 0

Weaponized: 0

Threat intel: +10

Gov advisory: 0

Attack Technique

Buffer Overflow HIGH

A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.

Remote Code Execution CRITICAL

Remote Code Execution represents the critical moment when an attacker successfully runs arbitrary code on a target system without physical access.