CVE-2025-20254
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 Internet Key Exchange Version 2 (IKEv2) module of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to trigger a memory leak, resulting in a denial of service (DoS) condition. This vulnerability is due to improper parsing of IKEv2 packets. An attacker could exploit this vulnerability by sending a continuous stream of crafted IKEv2 packets to an affected device. A successful exploit could allow the attacker to partially exhaust system memory, causing system instability like being unable to establish new IKEv2 VPN sessions. A manual reboot of the device is required to recover from this condition.
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 · high confidenceA vulnerability in the IKEv2 module of Cisco Secure Firewall ASA and FTD Software allows an unauthenticated remote attacker to trigger a memory leak by sending a continuous stream of improperly parsed IKEv2 packets, leading to partial memory exhaustion and inability to establish new VPN sessions.
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
- Low
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L
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.
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Identify the device model and software platformRun 'show version' or 'show inventory' on the ASA or FTD device to confirm it is Cisco Secure Firewall ASA or FTDAffected if Device is not Cisco ASA or FTD (not affected)
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Determine the installed software versionRun 'show version' and locate the ASA or FTD software version number (e.g., 9.x, 10.x)Affected if Version is within the range of affected releases as listed in the Cisco security advisory for CVE-2025-20254
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Verify if IKEv2 is enabledRun 'show crypto ikev2 sa' or check the VPN configuration via 'show run crypto' to see if any IKEv2 tunnel or policy is configuredAffected if IKEv2 is not configured or disabled (the vulnerability requires IKEv2 to be active)
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Confirm IKEv2 is exposed to untrusted networksReview the interface configuration ('show run interface') and ACLs applied to the outside-facing interface to determine if UDP port 500 or 4500 (IKEv2) is reachable from untrusted networksAffected if IKEv2 interface is not accessible from untrusted/unauthenticated sources (reduced exposure)
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Check current memory utilizationRun 'show memory' or 'show memory histogram' to observe current memory usage and check for unusually high consumptionAffected if Memory exhaustion is occurring or approaching limits, especially after periods of IKEv2 traffic
The environment is affected if the device runs a vulnerable ASA or FTD version, IKEv2 is actively configured, and the IKEv2 interface is exposed to untrusted networks where an attacker could send malicious IKEv2 packets.
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 vendor-supplied software update when available; until then, consider implementing network-level filtering to limit exposure of the IKEv2 interface to untrusted sources.
- Consultation3.0 h
- Implementation4.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-20254 — 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-2025-20254 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
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- Version or environment caveats, and links to real fixes
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