CVE-2025-20243
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA vulnerability in the management and VPN web servers of Cisco Secure Firewall ASA Software and Secure FTD Software could allow an unauthenticated, remote attacker to cause the device to reload unexpectedly, resulting in a DoS condition. This vulnerability is due to improper validation of user-supplied input on an interface with VPN web services. An attacker could exploit this vulnerability by sending crafted HTTP requests to a targeted web server on an affected device. A successful exploit could allow the attacker to cause a DoS condition when the device reloads.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceThis is an input validation vulnerability in the management and VPN web servers of Cisco ASA and FTD firewalls. An unauthenticated remote attacker can send specially crafted HTTP requests to the VPN web services interface, causing the device to reload unexpectedly due to improper validation of user-supplied input, resulting in denial of service.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Changed
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
-
Identify the Cisco device type and software versionLog into the device CLI and run 'show version' or check the ASA/FTD management interface to confirm the device model (ASA or FTD) and software version numberAffected if The device is a Cisco ASA or FTD firewall running any version (compare your version to Cisco's official advisory for CVE-2025-20243 to determine if it falls within the affected range)
-
Verify if VPN web services interface is enabledCheck the device configuration for VPN web services: on ASA use 'show running-config | include webvpn' or 'show running-config | include tunnel-general'; on FTD check via FMC or run 'show webvpn' in the CLIAffected if VPN web services (webvpn) is enabled on the device - this is the primary attack surface for this vulnerability
-
Confirm management web server statusRun 'show running-config http' or 'show running-config | include http' to check if the management web server is enabled and accessibleAffected if The management web interface (HTTP/HTTPS) is enabled and exposed, providing an attack vector
-
Assess network accessibility of the web interfacesReview access lists, security zone configurations, and interface policies to determine if the VPN web services or management web interfaces are reachable from untrusted networks (internet-facing or less-trusted zones)Affected if The VPN web services or management web interfaces are accessible from untrusted networks without adequate access controls
A user is affected if they are running a vulnerable version of Cisco ASA or FTD with VPN web services or management web interfaces enabled and accessible to the attacker.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataApply the Cisco patch when available; as a temporary measure, consider restricting access to management and VPN web interfaces via access lists or rate limiting to reduce attack surface.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,176.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-20243 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2025-20243 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data