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

Exp

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).

Published: 2020-02-05 Last update: 2025-10-28 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2020-3118 is rated Active Exploitation (73.8/100): CVSS High severity, with low exploitation likelihood (EPSS 0.18%). CISA KEV confirms active exploitation (added 2021-11-03) affecting Cisco / IOS XR. a weakness (CWE-134) Unauthenticated remote administrative access may be possible. The CISA remediation deadline has passed—treat as an emergency patch priority.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

CISA KEV Record for CVE-2020-3118

Name: Cisco IOS XR Software Discovery Protocol Format String Vulnerability · CISA KEV detail

Exploit added: 2021-11-03

Action due: 2022-05-03

Required action: Apply updates per vendor instructions.

Exploit prediction scoring system (EPSS) score for CVE-2020-3118

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-05 0.29% 0.18% -0.11%
2 2025-11-21 0.23% 0.29% +0.07%
3 2025-11-18 — 0.23% —

Full EPSS history (14 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2020-3118

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.8 3.1 HIGH
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:A)
Attacker has to be nearby on the network—same office, same link, that vibe—not the whole wide internet.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 5.9 [email protected]
8.8 3.0 HIGH
CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:A)
Attacker has to be nearby on the network—same office, same link, that vibe—not the whole wide internet.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 5.9 [email protected]
8.3 2.0 HIGH
AV:A/AC:L/Au:N/C:C/I:C/A:C Click to expand
Access vector (AV:A)
Requires access to an adjacent network segment.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:C)
Complete confidentiality impact.
Integrity impact (I:C)
Complete integrity impact.
Availability impact (A:C)
Complete availability impact.
 6.5 10.0 [email protected]

Weakness enumeration for CVE-2020-3118

Affected software / configurations for CVE-2020-3118

Vendor Product Version Raw CPE
cisco ios_xr >= 6.6.0, < 6.6.12 cpe:2.3:o:cisco:ios_xr:*:*:*:*:*:*:*:*
cisco ios_xr >= 7.0.0, < 7.0.2 cpe:2.3:o:cisco:ios_xr:*:*:*:*:*:*:*:*
cisco ios_xr 6.5.3 cpe:2.3:o:cisco:ios_xr:6.5.3:*:*:*:*:*:*:*
cisco ios_xr 5.2.5 cpe:2.3:o:cisco:ios_xr:5.2.5:*:*:*:*:*:*:*
cisco ios_xr 6.4.2 cpe:2.3:o:cisco:ios_xr:6.4.2:*:*:*:*:*:*:*
cisco ios_xr 6.6.25 cpe:2.3:o:cisco:ios_xr:6.6.25:*:*:*:*:*:*:*
cisco ios_xr 7.0.1 cpe:2.3:o:cisco:ios_xr:7.0.1:*:*:*:*:*:*:*

References for CVE-2020-3118

cvelogic Threat Intelligence