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Ios XeOperating system · Cisco

CVE-2017-12236

CRITICAL · 9.8 CVSS v3.0 Published 2017-09-29
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
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 the Locator/ID Separation Protocol (LISP) in Cisco IOS XE 3.2 through 16.5 could allow an unauthenticated, remote attacker using an x tunnel router to bypass authentication checks performed when registering an Endpoint Identifier (EID) to a Routing Locator (RLOC) in the map server/map resolver (MS/MR). The vulnerability is due to a logic error introduced via a code regression for the affected software. An attacker could exploit this vulnerability by sending specific valid map-registration requests, which will be accepted by the MS/MR even if the authentication keys do not match, to the affected software. A successful exploit could allow the attacker to inject invalid mappings of EIDs to RLOCs in the MS/MR of the affected software. This vulnerability affects Cisco devices that are configured with LISP acting as an IPv4 or IPv6 map server. This vulnerability affects Cisco IOS XE Software release trains 3.9E and Everest 16.4. Cisco Bug IDs: CSCvc18008.

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 logic error in Cisco IOS XE's LISP map-server implementation allows unauthenticated remote attackers to bypass authentication during EID-to-RLOC map registration. By sending specially crafted map-registration requests with mismatched authentication keys, attackers can inject false EID-to-RLOC mappings into the map server/map resolver, enabling traffic redirection or man-in-the-middle attacks.

MitigationApply Cisco IOS XE software updates that address CSCvc18008; alternatively, disable LISP map-server functionality if not required or restrict access to UDP port 4342 (LISP) at network boundaries.

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
Ios XeOperating system
Affected:= 3.2.0ja= 3.9.1e= 16.5.1c

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
High
Integrity
High
Availability
High

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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 XE version
    Execute 'show version' or 'show version | include IOS XE' to display the running software version
    Affected if The displayed version matches 3.2.0ja, 3.9.1e, or 16.5.1c exactly
  2. Determine if LISP is configured
    Execute 'show lisp session' or 'show ip lisp' to check for LISP configuration on the device
    Affected if LISP is configured and operational on the device
  3. Check if LISP map-server is enabled
    Execute 'show lisp map-server' or review the running configuration for 'lisp map-server' commands under the LISP router configuration mode
    Affected if LISP map-server functionality is enabled (the vulnerability only applies when map-server is active)
  4. Inspect LISP map-server authentication configuration
    Review the LISP map-server configuration using 'show running-config | include lisp' and check for authentication key settings under the map-server configuration
    Affected if LISP map-server is configured with authentication (the flaw allows bypass of this authentication)

A device is affected if it runs Cisco IOS XE version 3.2.0ja, 3.9.1e, or 16.5.1c AND has LISP map-server functionality enabled, regardless of authentication configuration.

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 IOS XE software updates that address CSCvc18008; alternatively, disable LISP map-server functionality if not required or restrict access to UDP port 4342 (LISP) at network boundaries.

Recommended fix Moderate confidence

Upgrade to IOS XE 16.5.2+ or 3.9.2+ (or later stable releases in respective trains)

  1. 1. Identify if the device is running Cisco IOS XE and configured with LISP as a map server/map resolver (MS/MR) using 'show lisp site' or 'show lisp map-server' commands
  2. 2. Check current IOS XE version with 'show version' command
  3. 3. Review Cisco security advisory cisco-sa-20171025-lisp for the complete list of fixed releases
  4. 4. Plan upgrade to a fixed IOS XE release (16.5.2 or later for the 16.5 train; 3.9.2 or later for the 3.9E train)
  5. 5. Back up current configuration using 'copy running-config startup-config' or 'archive config'
  6. 6. Upgrade IOS XE using standard Cisco upgrade procedures (TFTP, USB, or ROMmon)
  7. 7. After upgrade, verify LISP functionality with 'show lisp site' and confirm authentication is now properly enforced
  8. 8. Monitor logs for any unauthorized map-registration attempts
Caveat Standard IOS XE upgrade risks apply; test in lab environment first; some LISP configuration changes may be needed between major releases

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

Fix this in Ios Xe Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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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-2017-12236 in production — separate from our analysis above.

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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
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  • Version or environment caveats, and links to real fixes
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