CVE-2020-3118VulnerabilityPublished 11/03/2021Updated 10/24/2026

CVE-2020-3118: Cisco IOS XR Software Discovery Protocol Format String Vulnerability

Affects Cisco IOS XRSource CISA KEV

Severity

High

No CVSS score published yet

Exploitation: Actively exploited – in CISA KEV since 11/03/2021
KEV deadline: 05/03/2022
EPSS: 11.7% chance of exploitation in 30 days – higher than 96% of CVEs

What to do

CISA required action

Apply updates per vendor instructions.

nvd.nist.gov/vuln/detail/CVE-2020-3118 (opens in a new tab)

Description

CVE-2020-3118 is a vulnerability in Cisco IOS XR software where improper validation of string input in Cisco Discovery Protocol messages can allow an unauthenticated, adjacent attacker to execute code with administrative privileges or cause the device to reload. This vulnerability has been exploited in the wild.

Summary

Cisco IOS XR software improperly validates string input from certain fields in Cisco Discovery Protocol messages. This format string vulnerability (CWE-134) could be exploited by an unauthenticated attacker on an adjacent network to execute arbitrary code with administrative privileges or cause a device reload. The vulnerability has been observed in active exploitation scenarios.

Impact

Successful exploitation can lead to remote code execution with administrative privileges or cause the affected device to reload, resulting in denial of service. The attacker does not require authentication but must be adjacent to the vulnerable device's network.

Mitigation

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a patch is applied, restrict access to Cisco Discovery Protocol messages from untrusted adjacent networks to reduce exposure.

Weaknesses

CWE-134Unclassified weakness (opens in a new tab)

What to do

Description

AnalysisAI-generated, updated 10/24/2026, 09:27:43 UTC

Weaknesses

References

Related threats