CVE-2025-20333criticalunder attackCWE-120

CVE-2025-20333: critical vulnerability in Cisco Secure Firewall Adaptive Security…

Published · Updated

100Vexday Risk Score

Prioritize patching. It under exploitation confirmed by CISA and has a public proof of concept.

ssvc Actcvss 9.9epss 71%
from disclosure to weapon233 days
Published on NVDSep 25
1st PoC+233d
CISA KEVSep 25
exploitation probability
71%top 1% of all CVEs
observed exploitation
yesCISA + VulnCheck
2 public exploit(s)
Action required by CISAfederal deadline: 2025-09-26

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.

In short

A flaw in Cisco Secure Firewall's VPN web server fails to properly validate user input in web requests, allowing someone with valid VPN credentials to send malicious requests and run any code with root privileges on the device.

Technical detail

CWE-120 (buffer overflow/improper input validation) in the VPN web server of Cisco ASA and FTD allows authenticated remote attackers to execute arbitrary code with root privileges via crafted HTTP(S) requests. Exploitation requires valid VPN credentials and results in complete device compromise.

Summary generated and translated by AI from the official description.

The full analysis of this CVE is available in Portuguese →

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.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Affected products
Cisco · Cisco Secure Firewall Adaptive Security Appliance (ASA) SoftwareCisco · Cisco Secure Firewall Threat Defense (FTD) Software
public PoCs found — 2
githubgithub.com/curtishoughton/Cisco-ASA-CVE-2025-20333-Scanner★ 0vulncheckvulncheck.com/xdb/0484a4111572unverified
⚠ Public resources, to assess the exposure of systems you control or are authorized to test. Test only with authorization.
Related CVEs — Cisco Secure Firewall Adaptive Security…

In the same product, most dangerous first.

CVE-2025-20362MEDIUMCVE-2025-20362EPSS 87.1%KEVCVE-2026-20349HIGHCisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software Remote Access SSL VPN Denial of Service VulnerabilityEPSS 1.0%KEVCVE-2024-20358MEDIUMCVE-2024-20358EPSS 0.7%CVE-2026-20026MEDIUMMultiple Cisco Products Snort 3 DCERPC VulnerabilitiesEPSS 0.7%CVE-2026-20099MEDIUMCisco UCS Manager and FXOS Software Command Injection VulnerabilityEPSS 0.7%CVE-2026-20027MEDIUMCisco Snort DCERPC Stub Data Out of Bounds ReadEPSS 0.6%
References
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-webvpn-z5xP8EUBhttps://sec.cloudapps.cisco.com/security/center/resources/asa_ftd_continued_attackshttps://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-20333