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Openvpn CVE-2021-3824

MEDIUM
Improper Neutralization of Encoded URI Schemes in a Web Page (CWE-84)
2021-09-23 security@openvpn.net
6.1
CVSS 3.1 · NVD
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Vulnerability Assessment

Weakness
CWE
Impact

CVSS score of 6.1 (MEDIUM). Attack characteristics: network attack vector, low complexity, no privileges required, user interaction required.

Exploit ScenarioDerived

This vulnerability can be exploited remotely over the network. 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 0.7% exploitation probability (EPSS)

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AnalysisAI

OpenVPN Access Server 2.9.0 through 2.9.4 allow remote attackers to inject arbitrary web script or HTML via the web login page URL. Rated medium severity (CVSS 6.1), 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-84. OpenVPN Access Server 2.9.0 through 2.9.4 allow remote attackers to inject arbitrary web script or HTML via the web login page URL. Affected products include: Openvpn Openvpn Access Server. Version information: through 2.9.4.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 6.1 MEDIUM
AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

DescriptionNVD

OpenVPN Access Server 2.9.0 through 2.9.4 allow remote attackers to inject arbitrary web script or HTML via the web login page URL.

Threat Intelligence Overview

EPSS Score
0.7%
Top 50% 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 0.7%
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
Scheduled
Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
No
Human Impact· derived
Medium

Priority Score

31
Low Medium High Critical
KEV: 0
EPSS: +1
CVSS: +30
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Code Injection CRITICAL

Code injection occurs when an application accepts user input and passes it directly into a language interpreter or evaluator without proper sanitization.

Affected Products (CPE)NVD

cpe:2.3:a:openvpn:openvpn_access_server:*:*:*:*:*:*:*:*
CVE-2018-7544 CRITICAL POC
9.1 Mar 16

A cross-protocol scripting issue was discovered in the management interface in OpenVPN through 2.4.5. Rated critical sev

CVE-2017-7478 HIGH POC
7.5 May 15

OpenVPN version 2.3.12 and newer is vulnerable to unauthenticated Denial of Service of server via received large control

CVE-2020-9442 HIGH POC
7.8 Feb 28

OpenVPN Connect 3.1.0.361 on Windows has Insecure Permissions for %PROGRAMDATA%\OpenVPN Connect\drivers\tap\amd64\win10,

CVE-2018-9336 HIGH POC
7.8 May 01

openvpnserv.exe (aka the interactive service helper) in OpenVPN 2.4.x before 2.4.6 allows a local attacker to cause a do

CVE-2017-5868 MEDIUM POC
6.1 May 26

CRLF injection vulnerability in the web interface in OpenVPN Access Server 2.1.4 allows remote attackers to inject arbit

CVE-2014-9104 MEDIUM POC
6.8 Nov 26

Multiple cross-site request forgery (CSRF) vulnerabilities in the XML-RPC API in the Desktop Client in OpenVPN Access Se

CVE-2023-46850 CRITICAL
9.8 Nov 11

Use after free in OpenVPN version 2.6.0 to 2.6.6 may lead to undefined behavoir, leaking memory buffers or remote execut

CVE-2019-25429 MEDIUM POC
6.1 Feb 19

Comodo Dome Firewall 2.7.0 contains a reflected cross-site scripting vulnerability that allows attackers to inject malic

CVE-2019-25428 MEDIUM POC
6.1 Feb 19

Comodo Dome Firewall 2.7.0 contains multiple reflected cross-site scripting vulnerabilities in the openvpn_users endpoin

CVE-2017-12166 CRITICAL
9.8 Oct 04

OpenVPN versions before 2.3.3 and 2.4.x before 2.4.4 are vulnerable to a buffer overflow vulnerability when key-method 1

CVE-2024-1305 CRITICAL
9.8 Jul 08

tap-windows6 driver version 9.26 and earlier does not properly check the size data of incomming write operations which a

CVE-2024-27903 CRITICAL
9.8 Jul 08

OpenVPN plug-ins on Windows with OpenVPN 2.6.9 and earlier could be loaded from any directory, which allows an attacker

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