iOSOperating system · Cisco
CVE-2017-3864
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 DHCP client implementation of Cisco IOS (12.2, 12.4, and 15.0 through 15.6) and Cisco IOS XE (3.3 through 3.7) could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition. The vulnerability occurs during the parsing of a crafted DHCP packet. An attacker could exploit this vulnerability by sending crafted DHCP packets to an affected device that is configured as a DHCP client. A successful exploit could allow the attacker to cause a reload of an affected device, resulting in a DoS condition. This vulnerability affects Cisco devices that are running a vulnerable release of Cisco IOS or IOS XE Software and using a specific DHCP client configuration. Cisco Bug IDs: CSCuu43892.
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 DHCP client implementation of Cisco IOS (12.2, 12.4, 15.0-15.6) and Cisco IOS XE (3.3-3.7) allows an unauthenticated remote attacker to cause device reload by sending crafted DHCP packets to an affected device configured as a DHCP client. The vulnerability occurs during parsing of malformed DHCP packets.
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
>= 15.0, <= 15.6= 12.2= 12.4
Ios XeOperating system
>= 3.3, <= 3.7CVSS 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 device OS typeRun 'show version' and look for 'IOS' or 'IOS XE' in the output to determine if the device runs Cisco IOS or Cisco IOS XE.Affected if Device runs Cisco IOS or IOS XE
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Check installed IOS versionRun 'show version' and locate the version number (for example, 15.1(4)M or 12.2(33)SXI). Compare this version against the affected ranges: Cisco iOS 12.2, 12.4, or 15.0 through 15.6; Cisco IOS XE 3.3 through 3.7.Affected if Installed version falls within any of the affected ranges (12.2, 12.4, 15.0-15.6 for IOS, or 3.3-3.7 for IOS XE)
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Verify DHCP client is enabledRun 'show ip interface brief' and check for interfaces with 'DHCP' in the address column, or run 'show running-config | include ip address dhcp' to see DHCP client configuration.Affected if One or more interfaces are configured to obtain IP addresses via DHCP (DHCP client mode)
A device is affected if it runs a Cisco IOS or IOS XE version within the listed ranges AND has at least one interface configured as a DHCP client receiving packets from the network.
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 Cisco IOS/IOS XE software updates that address this vulnerability; alternatively, implement DHCP packet filtering at network edge to block malformed DHCP packets from reaching vulnerable DHCP client devices.
Fix this in iOS
Scoped from the published advisory
- Consultation6.0 h
- Implementation4.0 h
- Testing2.0 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 $4,128.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2017-3864 — 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-2017-3864 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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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
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