CVE-2023-25774Public exploitNetwork attack vector

Service interruption via TLS connection thread exhaustion

Published Oct 12, 2023 · Updated Aug 2, 2024

Resource exhaustion in SoftEther VPN 5.01.9674 and 5.02 allows remote attackers to crash the VPN server with repeated TLS connections. ConnectionAccept() creates a thread per accepted TCP connection, and TLS handshakes accumulate threads waiting on the shared Cedar lock until allocation calls Abort(). No authentication or user interaction is required; sustained connections can repeatedly restart the service and terminate existing VPN sessions.

CVSS severity7.5
High
EPSS probability0.73%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in SoftEther VPN 5.01.9674 and 5.02 allows remote attackers to crash the VPN server with repeated TLS connections. ConnectionAccept() creates a thread per accepted TCP connection, and TLS handshakes accumulate threads waiting on the shared Cedar lock until allocation calls Abort(). No authentication or user interaction is required; sustained connections can repeatedly restart the service and terminate existing VPN sessions.

The record

CVE
CVE-2023-25774
Published
Oct 12, 2023
Updated
Aug 2, 2024
Vendor
SoftEther VPN Project
Product
SoftEther VPN
Classifications
CWE-400, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 12, 2023CVE publishedPublication date reported by the CVE source.
  2. Aug 2, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5.01.9674
  2. Affected versionversion=5.02

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

SoftEther VPN Project · SoftEther VPNversion=5.01.9674; version=5.02

Published CVSS scores

7.5Cisco TalosCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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.

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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-400Uncontrolled Resource Consumption
T1499Endpoint Denial of Service

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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