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iOSOperating system · Cisco

CVE-2017-3850

MEDIUM · 5.9 CVSS v3.0 Published 2017-03-21
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
68/100
Remediation priority · Elevated
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 Autonomic Networking Infrastructure (ANI) feature of Cisco IOS Software (15.4 through 15.6) and Cisco IOS XE Software (3.7 through 3.18, and 16) could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition. The vulnerability is due to incomplete input validation on certain crafted packets. An attacker could exploit this vulnerability by sending a crafted IPv6 packet to a device that is running a Cisco IOS Software or Cisco IOS XE Software release that supports the ANI feature. A device must meet two conditions to be affected by this vulnerability: (1) the device must be running a version of Cisco IOS Software or Cisco IOS XE Software that supports ANI (regardless of whether ANI is configured); and (2) the device must have a reachable IPv6 interface. An exploit could allow the attacker to cause the affected device to reload. Cisco Bug IDs: CSCvc42729.

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 the Autonomic Networking Infrastructure (ANI) feature of Cisco IOS (15.4-15.6) and IOS XE (3.7-3.18, 16) allows unauthenticated remote attackers to cause denial of service via crafted IPv6 packets. The flaw stems from incomplete input validation on certain packets. Affected devices must be running an ANI-supporting software version (regardless of ANI configuration status) and have a reachable IPv6 interface. Successful exploitation causes the device to reload.

MitigationUpgrade to a Cisco patched software version per CSCvc42729. If upgrading is not immediately feasible, filter or block untrusted IPv6 traffic at network perimeter borders to reduce attack surface.

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:= 15.2\(3\)e= 15.2\(3\)e1= 15.2\(3\)e2= 15.2\(3\)e3= 15.2\(4\)e= 15.2\(4\)e1= 15.2\(4\)e2= 15.2\(5\)e= 15.2\(5b\)e= 15.3\(3\)s= 15.3\(3\)s1= 15.3\(3\)s2
Ios XeOperating system
Affected:= 3.7.0e= 3.7.1e= 3.7.2e= 3.7.3e= 3.7.4e= 3.7.5e= 3.8.0e= 3.8.1e= 3.8.2e= 3.8.3e= 3.9.0e= 3.9.1e

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
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.0/AV:N/AC:H/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 installed Cisco IOS or IOS XE version
    Run 'show version' on the device CLI and locate the version string (e.g., 'Version 15.3(3)s2' for IOS or 'Version 3.8.1e' for IOS XE)
    Affected if The version matches one of the affected versions listed: iOS 15.2(3)e through 15.3(3)s2, or IOS XE 3.7.0e through 3.9.1e
  2. Verify if IPv6 is enabled on any device interface
    Run 'show ipv6 interface brief' to list all interfaces with IPv6 addresses configured
    Affected if Any interface shows an IPv6 address (link-local or global), meaning the device has a reachable IPv6 interface
  3. Confirm IPv6 routing is active
    Run 'show ipv6 routers' or check that 'ipv6 unicast-routing' is present in the running configuration via 'show run | include ipv6 unicast-routing'
    Affected if IPv6 routing is enabled, making the device susceptible to crafted IPv6 packets

The device is affected if it runs an affected iOS/IOS XE version AND has any IPv6 interface that is reachable, regardless of whether Autonomic Networking Infrastructure (ANI) is explicitly configured.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade to a Cisco patched software version per CSCvc42729. If upgrading is not immediately feasible, filter or block untrusted IPv6 traffic at network perimeter borders to reduce attack surface.

Fix this in iOS Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
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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-2017-3850 in production — separate from our analysis above.

No notes yet

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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