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Firepower Threat Defense CVE-2023-20269

CRITICAL
Authentication Bypass Using an Alternate Path or Channel (CWE-288)
2023-09-06 psirt@cisco.com
9.1
CVSS 3.1 · NVD
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Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A07:2025 - Authentication Failures
ASVS 5.0
V6 - Authentication Alternate path authentication
Impact

CVSS score of 9.1 (CRITICAL). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required.

Exploit ScenarioDerived

This vulnerability can be exploited remotely over the network. Successful exploitation could compromise the critical-severity affected system.

Emergency Immediate action required. Why: CRITICAL + in CISA KEV (actively exploited), no patch available.
Exploited in the wild (CISA KEV) No patch listed yet 21.6% exploitation probability (EPSS)

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AnalysisAI

A vulnerability in the remote access VPN feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker. Rated critical severity (CVSS 9.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

Affects your stack

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Technical ContextAI · show details

This vulnerability is classified under CWE-288. A vulnerability in the remote access VPN feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to conduct a brute force attack in an attempt to identify valid username and password combinations or an authenticated, remote attacker to establish a clientless SSL VPN session with an unauthorized user. This vulnerability is due to improper separation of authentication, authorization, and accounting (AAA) between the remote access VPN feature and the HTTPS management and site-to-site VPN features. An attacker could exploit this vulnerability by specifying a default connection profile/tunnel group while conducting a brute force attack or while establishing a clientless SSL VPN session using valid credentials. A successful exploit could allow the attacker to achieve one or both of the following: Identify valid credentials that could then be used to establish an unauthorized remote access VPN session. Establish a clientless SSL VPN session (only when running Cisco ASA Software Release 9.16 or earlier). Notes: Establishing a client-based remote access VPN tunnel is not possible as these default connection profiles/tunnel groups do not and cannot have an IP address pool configured. This vulnerability does not allow an attacker to bypass authentication. To successfully establish a remote access VPN session, valid credentials are required, including a valid second factor if multi-factor authentication (MFA) is configured. Cisco will release software updates that address this vulnerability. There are workarounds that address this vulnerability. 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

NVD PRIMARY 9.1 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

Lifecycle Timeline

2
Added to CISA KEV
Jul 14, 2026 - 04:22 CISA
CVE Published
Sep 06, 2023 - 18:15 nvd
CRITICAL 9.1

DescriptionNVD

A vulnerability in the remote access VPN feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to conduct a brute force attack in an attempt to identify valid username and password combinations or an authenticated, remote attacker to establish a clientless SSL VPN session with an unauthorized user. This vulnerability is due to improper separation of authentication, authorization, and accounting (AAA) between the remote access VPN feature and the HTTPS management and site-to-site VPN features. An attacker could exploit this vulnerability by specifying a default connection profile/tunnel group while conducting a brute force attack or while establishing a clientless SSL VPN session using valid credentials. A successful exploit could allow the attacker to achieve one or both of the following: Identify valid credentials that could then be used to establish an unauthorized remote access VPN session. Establish a clientless SSL VPN session (only when running Cisco ASA Software Release 9.16 or earlier). Notes: Establishing a client-based remote access VPN tunnel is not possible as these default connection profiles/tunnel groups do not and cannot have an IP address pool configured. This vulnerability does not allow an attacker to bypass authentication. To successfully establish a remote access VPN session, valid credentials are required, including a valid second factor if multi-factor authentication (MFA) is configured. Cisco will release software updates that address this vulnerability. There are workarounds that address this vulnerability.

Threat Intelligence Overview

Threat Score
4.0/10
Composite threat intelligence
EPSS Score
21.6%
Top 3% exploitable
Threat Intel
1
1 source
Data Quality
4 sources
Confidence: Medium

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 21.6%
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
Yes
Human Impact· derived
High

Priority Score

128
Low Medium High Critical
KEV: +50
EPSS: +22
CVSS: +46
PoC: 0
Weaponized: 0
Threat intel: +10
Gov advisory: 0

Attack Technique

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

Affected Products (CPE)NVD

cpe:2.3:o:cisco:adaptive_security_appliance_software:9.8.1:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:9.8.1.5:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:9.8.1.7:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:9.8.2:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:9.8.2.8:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:9.8.2.14:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:9.8.2.15:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:9.8.2.17:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:9.8.2.20:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:9.8.2.24:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:9.8.2.26:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:9.8.2.28:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:9.8.2.33:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:9.8.2.35:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:9.8.2.38:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:9.8.3:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:9.8.3.8:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:9.8.3.11:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:9.8.3.14:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:9.8.3.16:*:*:*:*:*:*:*
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Threat IntelligenceMISP

CISA Advisories
Sources: CISA (public domain)

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