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Vulnerabilities

Vulnerability · CVE-2020-3118

Cisco IOS XR Software Discovery Protocol Format String Vulnerability

Published Feb 5, 2020 · catalog updated Jun 16, 2026 · Cisco IOS XR

Patch now

CVE-2020-3118 is in the CISA known-exploited catalog, due May 3, 2022. Confirm Cisco IOS XR against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Severity
High8.8
Known exploitation
CISA KEV and VulnCheck KEV
EPSS
11.68%
Remediation
Remediation guidance
Affected products
cpe cisco/ios xr · vendor Cisco IOS XR

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).

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe cisco/ios xr5.2.5
  • cpe cisco/ios xr6.4.2
  • cpe cisco/ios xr6.5.3
  • cpe cisco/ios xr6.6.25
  • cpe cisco/ios xr7.0.1
  • vendor Cisco IOS XRversion unspecified

How to fix CVE-2020-3118

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2020-3118 is in the CISA known-exploited catalog, due May 3, 2022. Confirm Cisco IOS XR against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Which versions are affected?

Compare what you have installed with cisco/ios xr 5.2.5; cisco/ios xr 6.4.2; cisco/ios xr 6.5.3; cisco/ios xr 6.6.25. Apply updates per vendor instructions.

What should an analyst verify?

CWE-134: Format String Vulnerability; CWE-787: Out-of-bounds Write. EPSS 11.68%. The CISA KEV listing is the exploitation evidence. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Cisco security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Feb 5, 2020 · Catalog

    Detected

    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 Cisc

  2. Nov 3, 2021 · CISA KEV

    Known exploited

    Apply updates per vendor instructions.

  3. May 3, 2022 · CISA KEV

    Remediation due

    Apply updates per vendor instructions.

  4. Jun 16, 2026 · Catalog

    Updated

    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 Cisc

Sources

  • CISA KEVConfirmed exploitationCVE-2020-3118

    Cisco IOS XR improperly validates string input from certain fields in Cisco Discovery Protocol messages. Exploitation could allow an unauthenticated, adjacent attacker to execute code with administrative privileges or cause a reload on an affected device.

    cisa.gov
  • CVE.orgVulnerability recordCVE-2020-3118

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2020-3118

    30-day exploitation probability 11.7%

    first.org
  • NIST NVDVulnerability recordCVE-2020-3118

    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 certa

    nvd.nist.gov
  • Packet Storm SecurityCited referencehttp://packetstormsecurity.com/files/156203/Cisco-Discovery-Protocol-CDP-Remote-Device-Takeover.html

    Packet Storm link already published on the finding.

    packetstormsecurity.com
  • VulnCheck KEVConfirmed exploitationCVE-2020-3118

    Cisco IOS XR improperly validates string input from certain fields in Cisco Discovery Protocol messages. Exploitation could allow an unauthenticated, adjacent attacker to execute code with administrative privileges or cause a reload on an affected device.

    vulncheck.com

References

Freshness

Last verified in this catalog Oct 17, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.