Cisco ASA/Firepower Threat Defense VPN Web Server buffer overflow

CVSS Meta Temp Score
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CTI Interest Score
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9.1$5k-$25k0.00

Summaryinfo

A vulnerability classified as critical has been found in Cisco ASA and Firepower Threat Defense. This affects an unknown function of the component VPN Web Server. Performing a manipulation results in buffer overflow. This vulnerability is known as CVE-2025-20333. Remote exploitation of the attack is possible. Furthermore, an exploit is available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in Cisco ASA and Firepower Threat Defense (version now known). It has been classified as critical. This affects some unknown processing of the component VPN Web Server. The manipulation with an unknown input leads to a buffer overflow vulnerability. CWE is classifying the issue as CWE-120. The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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.

The advisory is shared at sec.cloudapps.cisco.com. This vulnerability is uniquely identified as CVE-2025-20333 since 10/10/2024. The exploitability is told to be easy. It is possible to initiate the attack remotely. Technical details are unknown but an exploit is available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 10/29/2025).

It is declared as attacked. The vulnerability scanner Nessus provides a plugin with the ID 265943 (Cisco Secure Firewall Threat Defense Software VPN Web Server Remote Code Execution (cisco-sa-asaftd-webvpn-z5xP8EUB)), which helps to determine the existence of the flaw in a target environment. The CISA Known Exploited Vulnerabilities Catalog lists this issue since 09/25/2025 with a due date of 09/26/2025:

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 (U

Upgrading eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (265943) and CERT Bund (WID-SEC-2025-2142). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Affected

  • Cisco ASA (Adaptive Security Appliance)
  • Cisco Secure Firewall Threat Defense
  • Cisco IOS
  • Cisco IOS XE
  • Cisco IOS XR

Productinfo

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Vendor

Name

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 9.4
VulDB Meta Temp Score: 9.1

VulDB Base Score: 8.8
VulDB Temp Score: 8.4
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 9.9
CNA Vector (cisco): 🔒

CVSSv2info

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

Exploitinginfo

Class: Buffer overflow
CWE: CWE-120 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Attacked

EPSS Score: 🔒
EPSS Percentile: 🔒

KEV Added: 🔒
KEV Due: 🔒
KEV Remediation: 🔒
KEV Ransomware: 🔒
KEV Notice: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 265943
Nessus Name: Cisco Secure Firewall Threat Defense Software VPN Web Server Remote Code Execution (cisco-sa-asaftd-webvpn-z5xP8EUB)

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Timelineinfo

10/10/2024 CVE reserved
09/25/2025 +350 days Advisory disclosed
09/25/2025 +0 days VulDB entry created
10/29/2025 +33 days VulDB entry last update

Sourcesinfo

Vendor: cisco.com

Advisory: cisco-sa-asaftd-webvpn-z5xP8EUB
Status: Confirmed

CVE: CVE-2025-20333 (🔒)
GCVE (CVE): GCVE-0-2025-20333
GCVE (VulDB): GCVE-100-325905
CERT Bund: WID-SEC-2025-2142 - Cisco ASA, FTD, IOS, IOS XE, IOS XR: Mehrere Schwachstellen

scip Labs: https://www.scip.ch/en/?labs.20161013

Entryinfo

Created: 09/25/2025 19:10
Updated: 10/29/2025 00:05
Changes: 09/25/2025 19:10 (64), 09/25/2025 21:47 (13), 09/27/2025 07:40 (6), 09/27/2025 17:07 (2), 10/29/2025 00:05 (1)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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