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Nginx Controller CVE-2021-23020

MEDIUM
Use of Insufficiently Random Values (CWE-330)
2021-06-01 f5sirt@f5.com
5.5
CVSS 3.1 · NVD
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Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A04:2025 - Cryptographic Failures
ASVS 5.0
V11 - Cryptography Cryptographic random values
Impact

CVSS score of 5.5 (MEDIUM). Attack characteristics: local attack vector, low complexity, low privileges required, no user interaction not required.

Exploit ScenarioDerived

Successful exploitation could compromise the medium-severity affected system.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
No patch listed yet 0.3% exploitation probability (EPSS)

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AnalysisAI

The NAAS 3.x before 3.10.0 API keys were generated using an insecure pseudo-random string and hashing algorithm which could lead to predictable keys. Rated medium severity (CVSS 5.5), this vulnerability is 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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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-330. The NAAS 3.x before 3.10.0 API keys were generated using an insecure pseudo-random string and hashing algorithm which could lead to predictable keys. Affected products include: F5 Nginx Controller. Version information: before 3.10.0.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 5.5 MEDIUM
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

DescriptionNVD

The NAAS 3.x before 3.10.0 API keys were generated using an insecure pseudo-random string and hashing algorithm which could lead to predictable keys.

Threat Intelligence Overview

EPSS Score
0.3%
Top 83% exploitable
Data Quality
2 sources
Confidence: Low

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 MEDIUM
CISA KEV No
Public POC No
EPSS 0.3%
Patch available No
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
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
Defer
Exploitation· derived
None
System Exposure· derived
Small
Automatable· derived
No
Human Impact· derived
Medium

Priority Score

28
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +28
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

Affected Products (CPE)NVD

cpe:2.3:a:f5:nginx_controller:*:*:*:*:*:*:*:*
CVE-2020-27730 CRITICAL
9.8 Dec 11

In versions 3.0.0-3.9.0, 2.0.0-2.9.0, and 1.0.1, the NGINX Controller Agent does not use absolute paths when calling sys

CVE-2020-5901 CRITICAL
9.6 Jul 01

In NGINX Controller 3.3.0-3.4.0, undisclosed API endpoints may allow for a reflected Cross Site Scripting (XSS) attack.

CVE-2020-5900 HIGH
8.8 Jul 01

In versions 3.0.0-3.4.0, 2.0.0-2.9.0, and 1.0.1, there is insufficient cross-site request forgery (CSRF) protections for

CVE-2020-5863 HIGH
8.6 Mar 27

In NGINX Controller versions prior to 3.2.0, an unauthenticated attacker with network access to the Controller API can c

CVE-2020-5894 HIGH
8.1 May 07

On versions 3.0.0-3.3.0, the NGINX Controller webserver does not invalidate the server-side session token after users lo

CVE-2020-5867 HIGH
8.1 Apr 23

In versions prior to 3.3.0, the NGINX Controller Agent installer script 'install.sh' uses HTTP instead of HTTPS to check

CVE-2021-23019 HIGH
7.8 Jun 01

The NGINX Controller 2.0.0 thru 2.9.0 and 3.x before 3.15.0 Administrator password may be exposed in the systemd.txt fil

CVE-2020-5899 HIGH
7.8 Jul 01

In NGINX Controller 3.0.0-3.4.0, recovery code required to change a user's password is transmitted and stored in the dat

CVE-2020-5895 HIGH
7.8 May 07

On NGINX Controller versions 3.1.0-3.3.0, AVRD uses world-readable and world-writable permissions on its socket, which a

CVE-2020-5910 HIGH
7.5 Jul 02

In versions 3.0.0-3.5.0, 2.0.0-2.9.0, and 1.0.1, the Neural Autonomic Transport System (NATS) messaging services in use

CVE-2021-23018 HIGH
7.4 Jun 01

Intra-cluster communication does not use TLS. Rated high severity (CVSS 7.4), this vulnerability is remotely exploitable

CVE-2020-5864 HIGH
7.4 Apr 23

In versions of NGINX Controller prior to 3.2.0, communication between NGINX Controller and NGINX Plus instances skip TLS

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