Cisco ASA/Firepower Threat Defense SSL VPN memory leak

CVSS Meta Temp Score
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CTI Interest Score
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7.9$0-$5k0.00

Summaryinfo

A vulnerability classified as critical was found in Cisco ASA and Firepower Threat Defense. This vulnerability affects unknown code of the component SSL VPN. Such manipulation leads to memory leak. This vulnerability is referenced as CVE-2025-20133. It is possible to launch the attack remotely. No exploit is available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in Cisco ASA and Firepower Threat Defense (version unknown) and classified as critical. Affected by this issue is an unknown function of the component SSL VPN. The manipulation with an unknown input leads to a memory leak vulnerability. Using CWE to declare the problem leads to CWE-401. The product does not sufficiently track and release allocated memory after it has been used, which slowly consumes remaining memory. Impacted is availability. CVE summarizes:

A vulnerability in the management and VPN web servers of the Remote Access SSL VPN feature of Cisco Secure Firewall ASA Software and Secure FTD Software could allow an unauthenticated, remote attacker to cause the device to unexpectedly stop responding, resulting in a DoS condition. This vulnerability is due to ineffective validation of user-supplied input during the Remote Access SSL VPN authentication process. An attacker could exploit this vulnerability by sending a crafted request to the VPN service on an affected device. A successful exploit could allow the attacker to cause a DoS condition where the device stops responding to Remote Access SSL VPN authentication requests.

The advisory is shared for download at sec.cloudapps.cisco.com. This vulnerability is handled as CVE-2025-20133 since 10/10/2024. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 08/17/2025). The MITRE ATT&CK project declares the attack technique as T1499.

Upgrading eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at CERT Bund (WID-SEC-2025-1839). Once again VulDB remains the best source for vulnerability data.

Affected

  • Cisco ASA (Adaptive Security Appliance)

Productinfo

Type

Vendor

Name

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 8.0
VulDB Meta Temp Score: 7.9

VulDB Base Score: 7.5
VulDB Temp Score: 7.2
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 8.6
CNA Vector (cisco): 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Memory leak
CWE: CWE-401 / CWE-404
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Timelineinfo

10/10/2024 CVE reserved
08/14/2025 +308 days Advisory disclosed
08/14/2025 +0 days VulDB entry created
08/17/2025 +3 days VulDB entry last update

Sourcesinfo

Vendor: cisco.com

Advisory: cisco-sa-asaftd-vpn-dos-mfPekA6e
Status: Confirmed

CVE: CVE-2025-20133 (🔒)
GCVE (CVE): GCVE-0-2025-20133
GCVE (VulDB): GCVE-100-320180
CERT Bund: WID-SEC-2025-1839 - Cisco ASA und Secure Firewall Threat Defense: Mehrere Schwachstellen

Entryinfo

Created: 08/14/2025 19:44
Updated: 08/17/2025 07:29
Changes: 08/14/2025 19:44 (64), 08/17/2025 07:29 (7)
Complete: 🔍
Cache ID: 216::103

Once again VulDB remains the best source for vulnerability data.

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