dbcve.org
Ios XrOperating system · Cisco

CVE-2019-16018

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 →
72/100
Remediation priority · Elevated
Remotely reachable No privileges

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 Border Gateway Protocol (BGP) Ethernet VPN (EVPN) functionality in Cisco IOS XR Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition. The vulnerability is due to incorrect processing of a BGP update message that contains crafted EVPN attributes. An attacker could indirectly exploit the vulnerability by sending BGP EVPN update messages with a specific, malformed attribute to an affected system and waiting for a user on the device to display the EVPN operational routes’ status. If successful, the attacker could cause the BGP process to restart unexpectedly, resulting in a DoS condition. The Cisco implementation of BGP accepts incoming BGP traffic only from explicitly defined peers. To exploit this vulnerability, the malicious BGP update message would need to come from a configured, valid BGP peer, or would need to be injected by the attacker into the victim's BGP network on an existing, valid TCP connection to a BGP peer.

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 Cisco IOS XR Software's BGP EVPN implementation allows remote attackers to cause a denial of service by sending BGP update messages with malformed EVPN attributes. The vulnerability triggers an unexpected BGP process restart when a user displays EVPN operational route status. Exploitation requires the attacker to send the malicious message from a configured, valid BGP peer or inject it into an existing BGP TCP connection.

MitigationRestrict BGP peer access to trusted sources only, implement BGPsec or RPKI validation to filter invalid announcements, and apply Cisco IOS XR software updates when available to address the malformed attribute processing flaw.

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:= 6.6.1= 6.6.2= 6.6.25= 7.0.1

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
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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
    Execute 'show version' on the device and locate the IOS XR software release number in the output
    Affected if The version displayed matches 6.6.1, 6.6.2, 6.6.25, or 7.0.1 exactly
  2. Confirm BGP is configured
    Execute 'show bgp all' or 'show running-config | include router bgp' to verify BGP is enabled and has neighbor configurations
    Affected if BGP is actively configured with peers
  3. Verify EVPN address family is enabled under BGP
    Execute 'show bgp l2vpn evpn summary' or check the BGP configuration for 'address-family l2vpn evpn'
    Affected if EVPN address family is enabled under BGP
  4. Check for existing BGP EVPN routes
    Execute 'show bgp l2vpn evpn' to display EVPN routes in the BGP table
    Affected if EVPN routes are present in the BGP database

The device is affected if it runs IOS XR versions 6.6.1, 6.6.2, 6.6.25, or 7.0.1 AND has BGP with EVPN address family enabled and configured peers, because the malformed EVPN attribute vulnerability can be exploited from any valid BGP peer to trigger the denial of service condition.

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

Restrict BGP peer access to trusted sources only, implement BGPsec or RPKI validation to filter invalid announcements, and apply Cisco IOS XR software updates when available to address the malformed attribute processing flaw.

Fix this in Ios Xr Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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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-2019-16018 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
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  • No spam, self-promotion, credentials, or personal data