{"id":"CVE-2025-52570","aliases":["EUVD-2025-19032","GHSA-jpv7-p47h-f43j"],"status":"published","title":"Letmein connection limiter allows an arbitrary amount of simultaneous connections","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.","severity":{"version":"4.0","score":1.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U","level":"low","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00376,"percentile":0.31975,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-770","CWE-799"],"published":"2025-06-23T21:24:59Z","modified":"2026-11-11T02:47:50Z","fixes":[{"ecosystem":"crates.io","package":"letmeind","fixed_in":["10.2.1"],"sources":["ghsa","osv"]},{"ecosystem":"crates.io","package":"letmeinfwd","fixed_in":["10.2.1"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"crates.io","package":"letmeind","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"10.2.0"},{"fixed":"10.2.1"}]}]},{"source":"ghsa","ecosystem":"crates.io","package":"letmeinfwd","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"10.2.0"},{"fixed":"10.2.1"}]}]},{"source":"osv","ecosystem":"crates.io","package":"letmeind","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"10.2.1"}]}]},{"source":"osv","ecosystem":"crates.io","package":"letmeinfwd","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"10.2.1"}]}]}],"products":[{"vendor":"mbuesch","product":"letmein"}],"references":[{"url":"https://github.com/mbuesch/letmein/security/advisories/GHSA-jpv7-p47h-f43j","tags":["x_refsource_CONFIRM","advisory","web"]},{"url":"https://github.com/mbuesch/letmein/commit/43207cd77580410d97165d1e3c07361ba6f3558c","tags":["x_refsource_MISC","fix","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2025-52570","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-jpv7-p47h-f43j"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/52xxx/CVE-2025-52570.json","tags":["advisory"]},{"url":"https://github.com/mbuesch/letmein","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2025-52570","title":"Letmein connection limiter allows an arbitrary amount of simultaneous connections","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.","status":"published","published":"2025-06-24T03:13:29.37Z","modified":"2025-06-24T14:42:51.785Z","cvss":[{"version":"4.0","score":1.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U","level":"low","assessor":"cna"}],"cwes":["CWE-799","CWE-770"],"updated_at":"2026-11-02T14:32:31.309974Z"}],"euvd":[{"id":"EUVD-2025-19032","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.","status":"published","published":"2025-06-24T03:13:29Z","modified":"2025-06-24T14:42:51Z","cvss":[{"version":"4.0","score":1.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U","level":"low"}],"updated_at":"2026-11-02T20:32:17.4539Z"}],"ghsa":[{"id":"GHSA-jpv7-p47h-f43j","title":"letmein connection limiter allows an arbitrary amount of simultaneous connections","description":"### Impact\n\nThe connection limiter is implemented incorrectly.\nIt allows an arbitrary amount of simultaneously incoming connections (TCP, UDP and Unix socket) for the services `letmeind` and `letmeinfwd`.\nTherefore, the command line option `num-connections` is not effective and does not limit the number of simultaneously incoming connections.\n\n`letmeind` is the public network facing daemon (TCP/UDP).\n\n`letmeinfwd` is the internal firewall daemon that only listens on local Unix socket.\n\nPossible Denial Of Service by resource exhaustion.\n\n### Affected versions\nAll versions `\u003c= 10.2.0` are affected.\n\n### Patches\nAll users shall upgrade to version `10.2.1`.\n\n### Workarounds\n\nUntested possible workarounds:\n- It might be possible to limit the number of active connections to the `letmeind` port (default 5800) via firewall.\n- The resource consumption of the service might be restricted with a service manager such as systemd.\n\n### Severity:\n\nIf a (D)DoS is run against the service, *something* is going to be affected.\nThe connection limiter assures that the effect on the system itself is limited at the expense of the effect on the letmein services itself.\nSo even with the connection limiter active, a (D)DoS can lead to a less responsive or unresponsive letmein service.","status":"published","published":"2025-06-23T21:24:59Z","modified":"2025-06-27T23:08:47Z","cvss":[{"version":"4.0","score":4.6,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U","level":"medium"}],"cwes":["CWE-770"],"updated_at":"2026-11-02T14:38:48.783737Z"}],"nvd":[{"id":"CVE-2025-52570","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.","status":"published","published":"2025-06-24T04:15:50.36Z","modified":"2026-06-17T09:36:41.96Z","cvss":[{"version":"4.0","score":1.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"low","assessor":"secondary"}],"cwes":["CWE-770","CWE-799"],"updated_at":"2026-11-02T14:11:14.091082Z"}],"osv":[{"id":"CVE-2025-52570","title":"Letmein connection limiter allows an arbitrary amount of simultaneous connections","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.","status":"published","published":"2025-06-24T03:13:29.37Z","modified":"2026-11-11T10:47:19.362439921Z","cvss":[{"version":"4.0","score":1.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U","level":"low"}],"cwes":["CWE-770","CWE-799"],"updated_at":"2026-11-11T03:22:28.447808Z"},{"id":"GHSA-jpv7-p47h-f43j","title":"letmein connection limiter allows an arbitrary amount of simultaneous connections","description":"### Impact\n\nThe connection limiter is implemented incorrectly.\nIt allows an arbitrary amount of simultaneously incoming connections (TCP, UDP and Unix socket) for the services `letmeind` and `letmeinfwd`.\nTherefore, the command line option `num-connections` is not effective and does not limit the number of simultaneously incoming connections.\n\n`letmeind` is the public network facing daemon (TCP/UDP).\n\n`letmeinfwd` is the internal firewall daemon that only listens on local Unix socket.\n\nPossible Denial Of Service by resource exhaustion.\n\n### Affected versions\nAll versions `\u003c= 10.2.0` are affected.\n\n### Patches\nAll users shall upgrade to version `10.2.1`.\n\n### Workarounds\n\nUntested possible workarounds:\n- It might be possible to limit the number of active connections to the `letmeind` port (default 5800) via firewall.\n- The resource consumption of the service might be restricted with a service manager such as systemd.\n\n### Severity:\n\nIf a (D)DoS is run against the service, *something* is going to be affected.\nThe connection limiter assures that the effect on the system itself is limited at the expense of the effect on the letmein services itself.\nSo even with the connection limiter active, a (D)DoS can lead to a less responsive or unresponsive letmein service.","status":"published","published":"2025-06-23T21:24:59Z","modified":"2025-06-27T23:08:47Z","cvss":[{"version":"4.0","score":4.6,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U","level":"medium"}],"cwes":["CWE-770"],"updated_at":"2026-11-02T15:46:50.687609Z"}]}}