dbcve.org
Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 17 Mar 2022.
iOSOperating system · Cisco

CVE-2018-0159

HIGH · 7.5 CVSS v3.1 Published 2018-03-28
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
In the wild Remotely reachable No privileges Zero-click

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 · unedited
A vulnerability in the implementation of Internet Key Exchange Version 1 (IKEv1) functionality in Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause an affected device to reload, resulting in a denial of service (DoS) condition. The vulnerability is due to improper validation of specific IKEv1 packets. An attacker could exploit this vulnerability by sending crafted IKEv1 packets to an affected device during an IKE negotiation. A successful exploit could allow the attacker to cause an affected device to reload, resulting in a DoS condition. Cisco Bug IDs: CSCuj73916.

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 confidence

A vulnerability in Cisco IOS and IOS XE Software's IKEv1 implementation allows unauthenticated remote attackers to cause device reloads. The flaw stems from improper validation of crafted IKEv1 packets sent during IKE negotiation, leading to a denial of service condition.

MitigationApply Cisco security updates for CSCuj73916. If immediate patching is not possible, consider disabling IKEv1 or restricting IKE traffic to trusted sources via access control lists.

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
iOSOperating system
Affected:= 15.3\(3\)s
Ios XeOperating system
Affected:= 15.3\(3\)s

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
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify the Cisco IOS or IOS XE version
    Run 'show version' and look for the software version number (e.g., 15.3(3)s). Compare your version to the affected range: versions 15.3(3)s and below are affected.
    Affected if The installed version is 15.3(3)s or any earlier 15.x release in the 15.3 train.
  2. Confirm IKEv1 is enabled
    Run 'show running-config | include crypto isakmp' or 'show crypto isakmp sa' to see if IKEv1 (ISAKMP) policies or security associations are configured.
    Affected if IKEv1 policies exist in the configuration or active IKEv1 security associations are present.
  3. Verify IKEv1 is listening on external interfaces
    Check interface configurations with 'show ip interface' and look for UDP port 500 (IKE) exposure, or review ACLs applied to WAN/internet-facing interfaces.
    Affected if The device accepts IKEv1 traffic on any interface that is reachable from untrusted networks (such as WAN/Internet interfaces).

A device is affected if it runs Cisco IOS or IOS XE version 15.3(3)s or below, has IKEv1 enabled, and can receive unauthenticated IKEv1 packets from untrusted sources.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply Cisco security updates for CSCuj73916. If immediate patching is not possible, consider disabling IKEv1 or restricting IKE traffic to trusted sources via access control lists.

Recommended fix Moderate confidence

Upgrade to a fixed Cisco IOS/IOS XE release as specified in the Cisco Security Advisory CSCuj73916 (contact Cisco for specific fixed version for your train)

  1. 1. Identify the current Cisco IOS or IOS XE version on the affected device using 'show version' command.
  2. 2. Consult the Cisco Security Advisory for CVE-2018-0159 (CSCuj73916) on tools.cisco.com to obtain the complete list of affected versions and fixed releases.
  3. 3. Plan an upgrade to a fixed Cisco IOS or IOS XE release that resolves this vulnerability. Ensure the target release is compatible with your hardware platform.
  4. 4. Before upgrading in production, test the new IOS/IOS XE version in a lab environment to verify compatibility with your network configuration and dependent services.
  5. 5. Back up the current device configuration before performing the upgrade.
  6. 6. Upgrade the device to the fixed release using standard Cisco upgrade procedures (e.g., 'archive download-sw' for IOS or appropriate ROMMON/FPGA upgrades for IOS XE).
  7. 7. After upgrade, verify the device boots correctly and reloads properly.
  8. 8. Confirm the new version is running using 'show version' and test IKEv1 functionality if applicable.
Caveat Review Cisco's release notes for your target version for any feature changes or command syntax modifications that may affect your configuration

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in iOS Exploited in the wild — priority engagement
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
Get help mitigating

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 locally
dbcve dependency scanner

Check whether your project pulls in CVE-2018-0159 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2018-0159 in production — separate from our analysis above.

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.

What this is

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.

What belongs here
  • 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