Summary
letmein connection limiter allows an arbitrary amount of simultaneous connections
Affected versions
All versions <= 10.2.0 are affected.
Workarounds
Untested possible workarounds:
- It might be possible to limit the number of active connections to the
letmeindport (default 5800) via firewall. - The resource consumption of the service might be restricted with a service manager such as systemd.
Severity:
If a (D)DoS is run against the service, something is going to be affected.
The connection limiter assures that the effect on the system itself is limited at the expense of the effect on the letmein services itself.
So even with the connection limiter active, a (D)DoS can lead to a less responsive or unresponsive letmein service.
Impact
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.
letmeind is the public network facing daemon (TCP/UDP).
letmeinfwd is the internal firewall daemon that only listens on local Unix socket.
Possible Denial Of Service by resource exhaustion.
The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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All users shall upgrade to version 10.2.1.
Frequently Asked Questions
- What is CVE-2025-52570? CVE-2025-52570 is a medium-severity allocation of resources without limits or throttling vulnerability in letmeind (rust), affecting versions <= 10.2.0. It is fixed in 10.2.1. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
- Which packages are affected by CVE-2025-52570?
letmeind(rust) (versions <= 10.2.0)letmeinfwd(rust) (versions <= 10.2.0)
- Is there a fix for CVE-2025-52570? Yes. CVE-2025-52570 is fixed in 10.2.1. Upgrade to this version or later.
- Is CVE-2025-52570 exploitable, and should I be worried? Whether CVE-2025-52570 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2025-52570 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2025-52570?
- Upgrade
letmeindto 10.2.1 or later - Upgrade
letmeinfwdto 10.2.1 or later
- Upgrade