What is the CVSS score of CVE-2021-34714?

CVE-2021-34714 has a CVSS 3.1 base score of 7.4 (High). CVSS vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H. EPSS exploitation probability: 0.4%.

Fxos CVE-2021-34714

HIGH

Improper Input Validation (CWE-20)

2021-09-23 psirt@cisco.com

Denial Of Service Apple iOS Cisco Ios Xe Ios Xr Nx Os Firepower Extensible Operating System Fxos

7.4

CVSS 3.1 · NVD

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Vulnerability Assessment

Weakness	CWE CWE-20 OWASP Top 10:2025 A05:2025 - Injection ASVS 5.0 V2 - Validation and Business Logic Input validation, allowlisting
Impact	CVSS score of 7.4 (HIGH). Attack characteristics: adjacent network attack vector, low complexity, no privileges required, no user interaction not required.
Exploit ScenarioDerived	Successful exploitation could compromise the high-severity affected system.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).

No patch listed yet 0.4% exploitation probability (EPSS)

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AnalysisAI

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. Rated high severity (CVSS 7.4), this vulnerability is no authentication required, low attack complexity. No vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

Affects your stack

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Technical ContextAI · show details

This vulnerability is classified under CWE-20. 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. Affected products include: Cisco Fxos, Cisco Firepower Extensible Operating System, Cisco Ios, Cisco Ios Xe, Cisco Ios Xr.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 7.4 HIGH

AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Adjacent

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Changed

Confidentiality

None

Integrity

None

Availability

High

DescriptionNVD

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.

Threat Intelligence Overview

EPSS Score

0.4%

Top 70% exploitable

Data Quality

2 sources

Confidence: Low

NVD

CVE.org

EPSS

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity HIGH

CISA KEV No

Public POC No

EPSS 0.4%

Patch available No

Active threat No

Deciding rule

HIGH severity (CVSS 7.0-8.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

None

System Exposure· derived

Controlled

Automatable· derived

Human Impact· derived

Medium

Priority Score

Low Medium High Critical

KEV: 0

EPSS: 0

CVSS: +37

PoC: 0

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Denial of Service MEDIUM

Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.

Affected Products (CPE)NVD

cpe:2.3:o:cisco:fxos:*:*:*:*:*:*:*:*

cpe:2.3:o:cisco:firepower_extensible_operating_system:*:*:*:*:*:*:*:*

cpe:2.3:o:cisco:ios:*:*:*:*:*:*:*:*

cpe:2.3:o:cisco:ios_xe:*:*:*:*:*:*:*:*

cpe:2.3:o:cisco:ios_xr:*:*:*:*:*:*:*:*

cpe:2.3:o:cisco:nx-os:*:*:*:*:*:*:*:*

cpe:2.3:o:cisco:firepower_extensible_operating_system:*:*:*:*:*:*:*:*

cpe:2.3:o:cisco:ios:*:*:*:*:*:*:*:*

cpe:2.3:o:cisco:ios_xe:*:*:*:*:*:*:*:*

cpe:2.3:o:cisco:ios_xr:*:*:*:*:*:*:*:*

cpe:2.3:o:cisco:nx-os:*:*:*:*:*:*:*:*

cpe:2.3:o:cisco:firepower_extensible_operating_system:*:*:*:*:*:*:*:*

cpe:2.3:o:cisco:ios:*:*:*:*:*:*:*:*

cpe:2.3:o:cisco:ios_xe:*:*:*:*:*:*:*:*

+ 12 more

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References

Advisories & patches

ADVISORY https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ios-nxos-xr-udld-dos-W5hGHgtQ

Search Externally

GitHub PoC

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