CVE-2021-31604Public exploitNetwork attack vector

VPN client disconnection via tokenless POST

Published Sep 27, 2021 · Updated Aug 3, 2024

CSRF in furlongm openvpn-monitor 1.1.3 and earlier allows remote attackers to disconnect any VPN client through a victim's browser. The root POST handler accepts vpn_id, ip, port, and client_id without a CSRF token, then sends a client-kill or kill command to the OpenVPN management socket. Exploitation requires a user with network access to the monitor to open an attacker-controlled page; knowing or guessing a client ID is sufficient.

CVSS severity6.5
Medium
EPSS probability0.68%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

CSRF in furlongm openvpn-monitor 1.1.3 and earlier allows remote attackers to disconnect any VPN client through a victim's browser. The root POST handler accepts vpn_id, ip, port, and client_id without a CSRF token, then sends a client-kill or kill command to the OpenVPN management socket. Exploitation requires a user with network access to the monitor to open an attacker-controlled page; knowing or guessing a client ID is sufficient.

The record

CVE
CVE-2021-31604
Published
Sep 27, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-352, CAPEC-62
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 27, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:N/A:P
4.7Compass SecurityCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:N/A:L
6.9GitHubCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-352Cross-Site Request Forgery (CSRF)
CAPEC-62Cross Site Request Forgery

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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