dbcve.org
Ios XrOperating system · Cisco

CVE-2018-0241

HIGH · 7.4 CVSS v3.0 Published 2018-04-19
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 UDP broadcast forwarding function of Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition on the affected device. The vulnerability is due to improper handling of UDP broadcast packets that are forwarded to an IPv4 helper address. An attacker could exploit this vulnerability by sending multiple UDP broadcast packets to the affected device. An exploit could allow the attacker to cause a buffer leak on the affected device, eventually resulting in a DoS condition requiring manual intervention to recover. This vulnerability affects all Cisco IOS XR platforms running 6.3.1, 6.2.3, or earlier releases of Cisco IOS XR Software when at least one IPv4 helper address is configured on an interface of the device. Cisco Bug IDs: CSCvi35625.

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 buffer leak vulnerability exists in Cisco IOS XR Software's UDP broadcast forwarding function when forwarding UDP broadcast packets to IPv4 helper addresses. An unauthenticated adjacent attacker can exploit this by sending multiple UDP broadcast packets, causing a buffer leak that leads to a DoS condition requiring manual intervention to recover.

MitigationApply the Cisco software update for CSCvi35625 when available. Alternatively, review and remove unnecessary IPv4 helper address configurations on interfaces to reduce attack surface until the fix can be deployed.

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:= 4.0.4.base= 4.1.3.base= 4.2.4.base= 4.3.4.base= 4.4.3.ce= 5.0.3.ce= 5.1.4.base= 5.2.5.ce= 5.3.4.base= 5.4.3.ce= 6.0.4.base= 6.1.4.base

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. Identify the device OS and version
    Run 'show version' or check the system to confirm the device runs Cisco IOS XR and note the exact version string
    Affected if The IOS XR version matches one of the affected versions listed (4.0.4.base through 6.1.4.base)
  2. Locate IPv4 helper address configurations
    Use 'show running-config' or interface configuration mode to search for 'ip helper-address' statements under interface configurations
    Affected if Any interface has an IPv4 helper-address configured, enabling the UDP broadcast forwarding function
  3. Verify UDP broadcast forwarding is active
    Check interface configurations for active helper-address entries or use 'show ip helper-address' if available on the platform
    Affected if IPv4 helper addresses are actively configured and the device is forwarding UDP broadcasts to those addresses
  4. Confirm adjacent network accessibility
    Assess whether unauthenticated adjacent attackers can reach the device with UDP broadcast packets on the segment(s) with helper-address configurations
    Affected if The device's interfaces with helper-address configured are accessible to untrusted adjacent attackers who can send UDP broadcast packets

The device is affected if it runs a Cisco IOS XR version in the listed affected range AND has IPv4 helper-address configured on any interface, allowing an adjacent attacker to trigger the buffer leak via UDP broadcast packets.

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 Cisco software update for CSCvi35625 when available. Alternatively, review and remove unnecessary IPv4 helper address configurations on interfaces to reduce attack surface until the fix can be deployed.

Fix this in Ios Xr Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA2.0 h
15.0 hours of engineering $2,640
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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-2018-0241 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