What is the CVSS score of CVE-2020-3284?

CVE-2020-3284 has a CVSS 3.1 base score of 9.8 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 2.8%.

Ios Xr CVE-2020-3284

CRITICAL

Improper Access Control (CWE-284)

2020-11-06 psirt@cisco.com

Authentication Bypass Apple Cisco Ios Xr A9K Rsp880 Se Firmware A9K Rsp880 Tr Firmware A99 Rp2 Se Firmware A99 Rp2 Tr Firmware A99 Rsp Se Firmware A99 Rsp Tr Firmware A9K Rsp880 Lt Se Firmware A9K Rsp880 Lt Tr Firmware Asr 9901 Rp Firmware A99 Rp3 Se Firmware A99 Rp3 Tr Firmware A9K Rsp5 Se Firmware A9K Rsp5 Tr Firmware Ncs1001 Firmware Ncs1002 Firmware Ncs1004 Firmware N540 12Z20G Sys A D Firmware N540 24Z8Q2C M Firmware N540 28Z4C Sys A D Firmware N540 Acc Sys Firmware N540X 16Z4G8Q2C A D Firmware N540X 12Z16G Sys A D Firmware N560 4 Sys Firmware N560 7 Sys Firmware Ncs5001 Firmware Ncs5002 Firmware Ncs5011 Firmware Nc55 Rp Firmware Nc55 Rp E Firmware Ncs 5501 Firmware Ncs 5501 Se Firmware Ncs 5502 Firmware Ncs 5502 Se Firmware Ncs 55A2 Mod S Firmware Ncs 55A2 Mod Hd S Firmware Ncs 55A2 Mod Hx S Firmware Ncs 55A2 Mod Se S Firmware Ncs 55A2 Mod Se H S Firmware Ncs 55A1 36H Se S Firmware Ncs 55A1 36H S Firmware Ncs 55A1 24H Firmware Ncs55 A1 48Q6H Firmware Ncs 55A1 24Q6H S Firmware

9.8

CVSS 3.1 · NVD

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Vulnerability Assessment

Weakness	CWE CWE-284 OWASP Top 10:2025 A01:2025 - Broken Access Control ASVS 5.0 V8 - Authorization Access control enforcement MITRE ATT&CK 1 technique across 1 tactic: Defense Evasion The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Impact	CVSS score of 9.8 (CRITICAL). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required.
Exploit ScenarioDerived	This vulnerability can be exploited remotely over the network. Successful exploitation could compromise the critical-severity affected system.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.

No patch listed yet 2.8% exploitation probability (EPSS)

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AnalysisAI

A vulnerability in the enhanced Preboot eXecution Environment (PXE) boot loader for Cisco IOS XR 64-bit Software could allow an unauthenticated, remote attacker to execute unsigned code during the. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, 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

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified under CWE-284. A vulnerability in the enhanced Preboot eXecution Environment (PXE) boot loader for Cisco IOS XR 64-bit Software could allow an unauthenticated, remote attacker to execute unsigned code during the PXE boot process on an affected device. The PXE boot loader is part of the BIOS and runs over the management interface of hardware platforms that are running Cisco IOS XR Software only. The vulnerability exists because internal commands that are issued when the PXE network boot process is loading a software image are not properly verified. An attacker could exploit this vulnerability by compromising the PXE boot server and replacing a valid software image with a malicious one. Alternatively, the attacker could impersonate the PXE boot server and send a PXE boot reply with a malicious file. A successful exploit could allow the attacker to execute unsigned code on the affected device. Note: To fix this vulnerability, both the Cisco IOS XR Software and the BIOS must be upgraded. The BIOS code is included in Cisco IOS XR Software but might require additional installation steps. For further information, see the Fixed Software section of this advisory. Affected products include: Cisco A9K-Rsp880-Se Firmware, Cisco Ios Xr, Cisco A9K-Rsp880-Tr Firmware, Cisco A99-Rp2-Se Firmware, Cisco A99-Rp2-Tr Firmware.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 9.8 CRITICAL

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

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

DescriptionNVD

A vulnerability in the enhanced Preboot eXecution Environment (PXE) boot loader for Cisco IOS XR 64-bit Software could allow an unauthenticated, remote attacker to execute unsigned code during the PXE boot process on an affected device. The PXE boot loader is part of the BIOS and runs over the management interface of hardware platforms that are running Cisco IOS XR Software only. The vulnerability exists because internal commands that are issued when the PXE network boot process is loading a software image are not properly verified. An attacker could exploit this vulnerability by compromising the PXE boot server and replacing a valid software image with a malicious one. Alternatively, the attacker could impersonate the PXE boot server and send a PXE boot reply with a malicious file. A successful exploit could allow the attacker to execute unsigned code on the affected device. Note: To fix this vulnerability, both the Cisco IOS XR Software and the BIOS must be upgraded. The BIOS code is included in Cisco IOS XR Software but might require additional installation steps. For further information, see the Fixed Software section of this advisory.

Threat Intelligence Overview

EPSS Score

2.8%

Top 15% 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 CRITICAL

CISA KEV No

Public POC No

EPSS 2.8%

Patch available No

Active threat No

Deciding rule

CRITICAL severity

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

Open

Automatable· derived

Yes

Human Impact· derived

Medium

Priority Score

Low Medium High Critical

KEV: 0

EPSS: +3

CVSS: +49

PoC: 0

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Authentication Bypass CRITICAL

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.