CVE-2025-52570 Letmein connection limiter allows an arbitrary amount of simultaneous connections
An attacker can exhaust resources by opening unlimited simultaneous connections because the connection limiter fails to enforce limits.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-52570?
CVE-2025-52570 is a low-severity denial of service vulnerability in mbuesch letmein, published on 24 Jun 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Letmein is an authenticating port knocker. Prior to version 10.2.1, The connection limiter is implemented incorrectly. It allows an arbitrary amount of simultaneously incoming connections (TCP, UDP and Unix socket) for the services letmeind and letmeinfwd. Therefore, the command line option num-connections is not effective and does not limit the number of simultaneously incoming connections. This issue has been patched in version 10.2.1.
Which versions are affected by CVE-2025-52570?
4 open source packages ship an affected version, including letmeind and letmeinfwd.
| Package | Affected | Fixed in |
|---|---|---|
letmeind crates.io | All versions | 10.2.1 |
letmeind crates.io | All versions | 10.2.1 |
letmeinfwd crates.io | All versions | 10.2.1 |
letmeinfwd crates.io | All versions | 10.2.1 |
How do I fix CVE-2025-52570?
Upgrade letmeind to 10.2.1 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-52570 being exploited?
There is no known exploitation of CVE-2025-52570 in the wild and no public exploit code.
Sources
Also known as GHSA-jpv7-p47h-f43j.