Home/CVE/A vulnerability in the Unidirectional Link Detection (UDLD) feature of Cisco FXOS Software, Cisco IOS Software, Cisco IO
CVE

CVE-2021-34714

A vulnerability in the Unidirectional Link Detection (UDLD) feature of Cisco FXOS Software, Cisco IOS Software, Cisco IO

A vulnerability in the Unidirectional Link Detection (UDLD) feature of Cisco FXOS Software, Cisco IOS Software, Cisco IOS XE Software, Cisco IOS XR Software, and Cisco NX-OS Software could allow an unauthenticated, adjacent attacker to cause an affected device to reload. This vulnerability is due to improper input validation of the UDLD packets. An attacker could exploit this vulnerability by sending specifically crafted UDLD packets to an affected device.

A successful exploit could allow the attacker to cause the affected device to reload, resulting in a denial of service (DoS) condition. Note: The UDLD feature is disabled by default, and the conditions to exploit this vulnerability are strict. An attacker must have full control of a directly connected device.

On Cisco IOS XR devices, the impact is limited to the reload of the UDLD process.

HIGH · CVSS 7.4 EPSS 0.00185
Schedule remediation
  • CVSS base score ≥ 7.0
Sigma rules0 YARA rules0
⬡

Weakness Classification

CWE-20Improper Input Validation
CWE-20Improper Input Validation
▤

Affected Products & Versions

31
cisco fxos>= 2.2 and < 2.2.2.148
cisco fxos>= 2.3 and < 2.3.1.216
cisco fxos>= 2.4 and < 2.4.1.273
cisco fxos>= 2.6 and < 2.6.1.224
cisco fxos>= 2.7 and < 2.7.1.143
cisco fxos>= 2.8 and < 2.8.1.143
cisco fxos>= 2.9 and < 2.9.1.135
cisco firepower extensible operating system<= 8.4\(3.115\)
▣

Scoring & Timeline

7.4
HIGH · CVSS v3.1 · psirt@cisco.com
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD23 Sep 2021 · 03:15 AM
CVSS VectorCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
SSVC triage · cisa-vulnrichment
Exploitation
none
Automatable
no
Technical impact
partial
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.
⚑

Vendor Advisories

1
cisco-csafcisco-sa-ios-nxos-xr-udld-dos-W5hGHgtQ
🔗

References & Sources

1
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ios-nxos-xr-udld-dos-W5hGHgtQVendor Advisory
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