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iOSOperating system · Cisco

CVE-2017-3849

HIGH · 7.4 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 →
79/100
Remediation priority · High
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) registrar feature of Cisco IOS Software (possibly 15.2 through 15.6) and Cisco IOS XE Software (possibly 3.7 through 3.18, and 16) could allow an unauthenticated, adjacent 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 autonomic network channel discovery packet to a device that has all the following characteristics: (1) running a Cisco IOS Software or Cisco IOS XE Software release that supports the ANI feature; (2) configured as an autonomic registrar; (3) has a whitelist configured. An exploit could allow the attacker to cause the affected device to reload. Note: Autonomic networking should be configured with a whitelist. Do not remove the whitelist as a workaround. Cisco Bug IDs: CSCvc42717.

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) registrar feature of Cisco IOS and IOS XE Software allows an unauthenticated, adjacent attacker to cause device reload (DoS) by sending crafted autonomic network channel discovery packets. The vulnerability stems from incomplete input validation on certain packets when the device is configured as an autonomic registrar with a whitelist.

MitigationApply the vendor patch from Cisco for affected IOS/IOS XE releases. Maintain the whitelist configuration (do not remove as a workaround). Implement network segmentation to restrict adjacent attacker access to the autonomic network segment.

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\(4\)e3= 15.2\(5\)e= 15.2\(5\)e1= 15.2\(5a\)e= 15.2\(5b\)e
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
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.0/AV:A/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 checks

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

  1. Check the Cisco IOS or IOS XE version
    Run 'show version' and locate the version string in the output. Compare it against the affected versions: IOS 15.2(3)e through 15.2(5b)e, or IOS XE 3.7.0e through 3.9.1e.
    Affected if The installed version matches one of the versions listed in the affected products and versions for this CVE.
  2. Verify Autonomic Networking feature is enabled
    Run 'show running-config | include autonomic' or 'show autonomic' to search for any autonomic-related configuration in the device.
    Affected if Any autonomic networking configuration is present on the device.
  3. Confirm the device is configured as an autonomic registrar
    Look for 'autonomic registrar' in the configuration output. Check for commands such as 'autonomic registrar enable' or similar registrar-related settings under the autonomic configuration context.
    Affected if The device is configured as an autonomic registrar.
  4. Check if a whitelist is configured on the registrar
    Look for whitelist entries in the autonomic registrar configuration, such as 'autonomic whitelist' or similar access control lists that define allowed devices.
    Affected if A whitelist configuration exists under the autonomic registrar settings.

The device is affected only if it runs a matching affected version AND is configured as an autonomic registrar with a whitelist; the vulnerability cannot be triggered if these specific conditions are not met.

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

Apply the vendor patch from Cisco for affected IOS/IOS XE releases. Maintain the whitelist configuration (do not remove as a workaround). Implement network segmentation to restrict adjacent attacker access to the autonomic network segment.

Fix this in iOS Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
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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-2017-3849 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