Adaptive Security Appliance SoftwareApplication · Cisco
CVE-2019-15256
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 1 (IKEv1) feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to trigger a reload of an affected device, resulting in a denial of service (DoS) condition. The vulnerability is due to improper management of system memory. An attacker could exploit this vulnerability by sending malicious IKEv1 traffic to an affected device. The attacker does not need valid credentials to authenticate the VPN session, nor does the attacker's source address need to match a peer statement in the crypto map applied to the ingress interface of the affected device. An exploit could allow the attacker to exhaust system memory resources, leading to a reload of an affected device.
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 confidenceA memory management vulnerability in Cisco ASA and FTD software's IKEv1 implementation allows an unauthenticated remote attacker to send malicious IKEv1 packets that exhaust system memory resources, causing the device to reload and resulting in denial of service. The attacker does not require valid credentials or a trusted peer address.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Adaptive Security Appliance SoftwareApplication
>= 9.7, < 9.8.4.10>= 9.9, < 9.9.2.47>= 9.10, < 9.10.1.30>= 9.12, < 9.12.2.5
Secure Firewall Threat DefenseApplication
>= 6.2.0, < 6.2.3.11>= 6.3.0, < 6.3.0.2
Asa 5505 FirmwareOperating system
= 9.9\(2.4\)= 201.4\(1.21\)
Asa 5510 FirmwareOperating system
= 9.9\(2.4\)= 201.4\(1.21\)
Asa 5512 X FirmwareOperating system
= 9.9\(2.4\)= 201.4\(1.21\)
Asa 5515 X FirmwareOperating system
= 9.9\(2.4\)= 201.4\(1.21\)
Asa 5520 FirmwareOperating system
= 9.9\(2.4\)= 201.4\(1.21\)
Asa 5525 X FirmwareOperating system
= 9.9\(2.4\)= 201.4\(1.21\)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.
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Identify the installed product typeDetermine whether the device is running Cisco ASA Software or Cisco Firepower Threat Defense (FTD). On the device console, use 'show version' to display the system software image name. Look for 'asa' or 'threat defense' in the output.Affected if Product is Cisco ASA or FTD software as listed in affected versions
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Determine the installed software versionExecute 'show version' on the device CLI and locate the software version number displayed next to 'Cisco Adaptive Security Appliance Software' or 'Firepower Threat Defense'. Compare this version string to the affected ranges: ASA >= 9.7, < 9.8.4.10; >= 9.9, < 9.9.2.47; >= 9.10, < 9.10.1.30; >= 9.12, < 9.12.2.5. FTD >= 6.2.0, < 6.2.3.11; >= 6.3.0, < 6.3.0.2.Affected if Installed version falls within any of the affected version ranges
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Check if IKEv1 is enabledUse the command 'show crypto isakmp sa' to display active IKEv1 security associations. Additionally, run 'show run crypto isakmp' to view the IKEv1 policy configuration. If any IKEv1 policies are defined or active SAs exist, IKEv1 is enabled.Affected if IKEv1 is enabled and configured on the device
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Verify IKEv1 exposure to untrusted networksReview the interface configuration using 'show run' and examine which interfaces have IKEv1 (ISAKMP) enabled. Check ACLs applied to external or internet-facing interfaces to determine whether IKEv1 traffic from untrusted sources is permitted. Use 'show crypto isakmp stats' to observe incoming IKEv1 packet activity.Affected if IKEv1 is enabled on an interface accessible from untrusted networks such as the internet, without ACL restrictions blocking inbound IKEv1 packets
Device is affected if it runs a vulnerable ASA or FTD version within the affected ranges, has IKEv1 enabled, and exposes IKEv1 to untrusted or external networks.
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 data6.2.3.116.3.0.29.8.4.10
Apply Cisco security updates for ASA and FTD software when available; consider implementing ACLs on external interfaces to restrict IKEv1 traffic to trusted sources as a defensive measure.
Fix this in Adaptive Security Appliance Software
Scoped from the published advisory
- Consultation3.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,408.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2019-15256 — 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-2019-15256 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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