# CVE-2023-27516: Auth bypass in SoftEther VPN

> An attacker can bypass authentication in SoftEther VPN by sending a specially crafted network packet, gaining unauthorized access to the system.

- **Severity:** High 7.3 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 12 Oct 2023
- **Updated:** 2 Aug 2024
- **Also known as:** GHSA-cw58-3hpw-976j

## What is CVE-2023-27516?

CVE-2023-27516 is a high-severity authentication bypass vulnerability in SoftEther VPN, published on 12 Oct 2023. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

An authentication bypass vulnerability exists in the CiRpcAccepted() functionality of SoftEther VPN 4.41-9782-beta and 5.01.9674. A specially crafted network packet can lead to unauthorized access. An attacker can send a network request to trigger this vulnerability.

Weakness: CWE-1188 (Initialization of a Resource with an Insecure Default), CWE-453 (Insecure Default Variable Initialization)

## Which versions are affected by CVE-2023-27516?

It affects 1 product.


Products: Softether Vpn.

## How do I fix CVE-2023-27516?

No fix has been published for CVE-2023-27516 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-27516 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-27516 exists.

## Other vulnerabilities in SoftEther VPN

- [CVE-2025-25565](https://insights.sbomify.com/CVE-2025-25565/): Memory corruption in n/a (critical 9.8)
- [CVE-2025-25567](https://insights.sbomify.com/CVE-2025-25567/): Memory corruption in n/a (critical 9.8)
- [CVE-2025-25568](https://insights.sbomify.com/CVE-2025-25568/): Use after free in n/a (critical 9.8)
- [CVE-2023-27395](https://insights.sbomify.com/CVE-2023-27395/): Memory corruption in SoftEther VPN (critical 9.0)
- [CVE-2023-32634](https://insights.sbomify.com/CVE-2023-32634/): Auth bypass in SoftEther VPN (high 7.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-27516 and fix it if it is affected.

What it is: CVE-2023-27516 is a high-severity authentication bypass vulnerability in SoftEther VPN, published on 12 Oct 2023. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-27516 exists.

Affected product: SoftEther VPN. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2023-27516/ (Markdown: https://insights.sbomify.com/CVE-2023-27516/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-27516
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-27516
- OSV: https://osv.dev/vulnerability/CVE-2023-27516

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-27516/
Summaries are generated and may contain mistakes; the official description above is the record.