dbcve.org
Ios XrOperating system · Cisco

CVE-2019-16027

MEDIUM · 6.5 CVSS v3.1 Published 2020-01-26
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
71/100
Remediation priority · Elevated
Remotely reachable 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 Intermediate System–to–Intermediate System (IS–IS) routing protocol functionality in Cisco IOS XR Software could allow an authenticated, remote attacker to cause a denial of service (DoS) condition in the IS–IS process. The vulnerability is due to improper handling of a Simple Network Management Protocol (SNMP) request for specific Object Identifiers (OIDs) by the IS–IS process. An attacker could exploit this vulnerability by sending a crafted SNMP request to the affected device. A successful exploit could allow the attacker to cause a DoS condition in the IS–IS process.

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

This vulnerability in Cisco IOS XR Software allows an authenticated, remote attacker to crash the IS-IS routing process by sending a crafted SNMP request targeting specific OIDs. The IS-IS process improperly handles these SNMP requests, causing a denial of service.

MitigationPrimary remediation is upgrading to a Cisco IOS XR Software version that includes the fix. As an interim mitigation, restrict SNMP access via ACLs, disable SNMP if not required, or limit SNMP to authenticated SNMPv3 with encryption.

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 XrOperating system
Affected:= 4.3.2= 5.2.5= 6.2.2= 6.2.3= 6.2.25= 6.3.3= 6.4.2= 6.1.3= 6.1.4= 6.5.2= 6.5.3= 6.3.15

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

CVSS:3.1/AV:N/AC:L/PR:L/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 Cisco IOS XR version
    Run 'show version' or 'admin show version' on the device to display the installed IOS XR software version
    Affected if The version matches one of these: 4.3.2, 5.2.5, 6.2.2, 6.2.3, 6.2.25, 6.3.3, 6.4.2, 6.1.3, 6.1.4, 6.5.2, 6.5.3, 6.3.15
  2. Verify SNMP is enabled
    Run 'show snmp' or check the configuration with 'show run | include snmp' to determine if SNMP is configured and running
    Affected if SNMP is enabled and accessible to the attacker (any SNMP community string that can be used)
  3. Confirm IS-IS routing process is configured
    Run 'show isis database' or 'show protocol isis' to check if the IS-IS protocol is enabled on any interface
    Affected if IS-IS is actively configured and running on the device
  4. Check SNMP access control
    Review SNMP configuration with 'show run | section snmp' and check for any ACLs applied to SNMP communities
    Affected if SNMP is exposed without restrictive ACLs or limited to unauthenticated SNMPv1/v2c

The device is affected if it runs a Cisco IOS XR version matching 4.3.2, 5.2.5, 6.2.2, 6.2.3, 6.2.25, 6.3.3, 6.4.2, 6.1.3, 6.1.4, 6.5.2, 6.5.3, or 6.3.15 AND has SNMP enabled AND has IS-IS configured, allowing a remote authenticated attacker to crash the IS-IS process via crafted SNMP requests.

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

Primary remediation is upgrading to a Cisco IOS XR Software version that includes the fix. As an interim mitigation, restrict SNMP access via ACLs, disable SNMP if not required, or limit SNMP to authenticated SNMPv3 with encryption.

Fix this in Ios Xr Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA2.0 h
16.0 hours of engineering $2,840
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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-2019-16027 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