dbcve.org
Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 3 May 2022.
Ios XrOperating system · Cisco

CVE-2020-3118

HIGH · 8.8 CVSS v3.1 Published 2020-02-05
Fix available
A fix is available. Upgrade to 6.6.12 / 7.0.2 or later.
See remediation →
99/100
Remediation priority · Urgent
In the wild Public exploit 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 Cisco Discovery Protocol implementation for Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to execute arbitrary code or cause a reload on an affected device. The vulnerability is due to improper validation of string input from certain fields in Cisco Discovery Protocol messages. An attacker could exploit this vulnerability by sending a malicious Cisco Discovery Protocol packet to an affected device. A successful exploit could allow the attacker to cause a stack overflow, which could allow the attacker to execute arbitrary code with administrative privileges on an affected device. Cisco Discovery Protocol is a Layer 2 protocol. To exploit this vulnerability, an attacker must be in the same broadcast domain as the affected device (Layer 2 adjacent).

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 stack buffer overflow vulnerability in Cisco IOS XR's Cisco Discovery Protocol (CDP) implementation allows an unauthenticated, Layer 2 adjacent attacker to inject malicious code via specially crafted CDP packets with improperly validated string fields, achieving arbitrary code execution with administrative privileges.

MitigationApply Cisco security patches for CVE-2020-3118; alternatively, disable CDP on vulnerable interfaces or implement Layer 2 network segmentation to restrict adjacency-based attacks.

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:>= 6.6.0, < 6.6.12>= 7.0.0, < 7.0.2= 6.5.3= 5.2.5= 6.4.2= 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
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:A/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 Cisco IOS XR version
    Run 'show version' or 'admin show version' to display the installed IOS XR version
    Affected if The displayed version matches any of these ranges: 6.6.0 through 6.6.11, 6.6.25, 7.0.1, 7.0.0 through 7.0.1, or is exactly 6.5.3, 5.2.5, or 6.4.2
  2. Verify CDP is enabled
    Run 'show cdp neighbor' or 'show cdp interface' to list interfaces with CDP enabled
    Affected if CDP is active on any interface - the vulnerability is only exploitable when CDP packets can be received
  3. Check CDP configuration
    Run 'show run | include cdp' or 'show running-config | include cdp' to see CDP global and interface-level configuration
    Affected if CDP is globally enabled or enabled on specific interfaces (cdp enable or no cdp disable appears in config)
  4. Confirm Layer 2 adjacency
    Review 'show cdp neighbor' output to identify adjacent devices that can send CDP packets to this device
    Affected if Any CDP neighbors are listed, meaning untrusted Layer 2 adjacent devices can reach this device with CDP messages

You are affected if the device runs a vulnerable Cisco IOS XR version listed above AND has CDP enabled on any interface accessible to untrusted Layer 2 neighbors.

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
Upgrade available Upgrade to 6.6.12 / 7.0.2 or later
Fixed in 6.6.127.0.2
Interim mitigation

Apply Cisco security patches for CVE-2020-3118; alternatively, disable CDP on vulnerable interfaces or implement Layer 2 network segmentation to restrict adjacency-based attacks.

Recommended fix High confidence

For 6.6.x: upgrade to 6.6.12 or later; For 7.0.x: upgrade to 7.0.2 or later; For 6.5.3/5.2.5: migrate to latest supported IOS XR release in respective train

  1. 1. Identify the current Cisco IOS XR version using 'show version' command
  2. 2. Based on current version, plan upgrade path: for 6.6.x line upgrade to 6.6.12 or later, for 7.0.x line upgrade to 7.0.2 or later
  3. 3. For versions 6.5.3 and 5.2.5, upgrade to the latest supported IOS XR release for that train
  4. 4. Download the appropriate Cisco IOS XR software image from Cisco.com (requires valid service contract)
  5. 5. Verify software image integrity using MD5/SHA256 checksum provided by Cisco
  6. 6. Schedule maintenance window as upgrade will cause device reload
  7. 7. Backup current configuration using 'copy running-config startup-config' or external TFTP/FTP server
  8. 8. Install the new IOS XR software package using 'install add' and 'install activate' commands, or upgrade via ROMMON if needed
Caveat Standard IOS XR upgrade may cause temporary service disruption; verify hardware compatibility and review Cisco release notes for any behavioral changes in specific version

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

Fix this in Ios Xr Exploited in the wild — priority engagement
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
Get it fixed fast

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,120.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2020-3118 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2020-3118 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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