Home/CVE/Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Buffer Overflow Vulnerability
CVE

CVE-2025-20333

Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Buffer Overflow Vulnerability

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.

CRITICAL · CVSS 9.9 ⚠ CISA KEV EPSS 0.29794
Act now
  • Listed on CISA KEV (known exploited in the wild)
  • SSVC exploitation status: active
  • EPSS ≥ 0.10 - elevated exploitation probability
  • EPSS percentile: top 3% of all CVEs by exploitation likelihood
  • CVSS base score ≥ 7.0
Sigma rules0 YARA rules0
⬢

Required Remediation

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.

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Weakness Classification

CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
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Affected Products & Versions

12
cisco adaptive security appliance software>= 9.12 and < 9.12.4.72
cisco adaptive security appliance software>= 9.14 and < 9.14.4.28
cisco adaptive security appliance software>= 9.16 and < 9.16.4.85
cisco adaptive security appliance software>= 9.17.0 and < 9.17.1.45
cisco adaptive security appliance software>= 9.18 and < 9.18.4.47
cisco adaptive security appliance software>= 9.19 and < 9.19.1.37
cisco adaptive security appliance software>= 9.20 and < 9.20.3.7
cisco adaptive security appliance software>= 9.22 and < 9.22.1.3
◈

Detection Rules (IDS/IPS)

1
et-openET WEB_SERVER Cisco ASA/FTD Authenticated Buffer Overflow (CVE-2025-20333)web-application-attack
Open rulesets (ET Open, Snort Community, abuse.ch) link to source. Commercial rulesets are reference-only.
▣

Scoring & Timeline

9.9
CRITICAL · CVSS v3.1 · psirt@cisco.com
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD25 Sep 2025 · 04:15 PM
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
SSVC triage · cisa-vulnrichment
Exploitation
active
Automatable
no
Technical impact
total
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.
⚑

Vendor Advisories

7
cisco-psirtcisco-sa-asaftd-persist-CISAED25-03
cisco-csafcisco-sa-asaftd-persist-CISAED25-03
cisaKEV-CVE-2025-20333
cisco-csafcisco-sa-asaftd-webvpn-YROOTUW
cisco-csafcisco-sa-asaftd-webvpn-z5xP8EUB
🔗

References & Sources

3
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-webvpn-z5xP8EUBVendor Advisory
https://sec.cloudapps.cisco.com/security/center/resources/asa_ftd_continued_attacksVendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-20333US Government Resource
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