{"schema_version":"1.9.0","id":"EEF-CVE-2026-42792","published":"2026-07-27T14:58:24.426Z","modified":"2026-09-08T08:04:01.427518Z","aliases":["CVE-2026-42792","GHSA-h6f3-hx58-xhj6"],"summary":"epmd permanent DoS via EMFILE on accept(2) in erts","details":"## Summary\n\nImproper Handling of Exceptional Conditions vulnerability in Erlang OTP erts (epmd) allows an unauthenticated remote attacker to permanently terminate the Erlang Port Mapper Daemon (epmd) via connection slot exhaustion.\n\nThe do\\_accept function in erts/epmd/src/epmd\\_srv.c calls epmd\\_cleanup\\_exit() when accept(2) returns EMFILE (per-process file descriptor limit reached) or ENFILE (system-wide file descriptor limit reached), rather than treating these as recoverable conditions. An attacker can exhaust epmd's file descriptor slots by holding many TCP connections open while periodically sending a single byte to reset the idle timeout, then causing accept(2) to return EMFILE, which kills the daemon. epmd has no per-source-IP connection cap, making the attack feasible from a single source.\n\nOn Debian/Ubuntu default packaging the impact is amplified: the systemd unit inherits a low file descriptor soft limit, and repeated daemon deaths trigger systemd's start-rate-limit, permanently failing both epmd.service and epmd.socket and requiring manual operator intervention to recover.\n\nThis issue affects OTP from OTP 17.0 before OTP 29.0.4, OTP 28.5.0.4 and OTP 27.3.4.15.\n\n## Workarounds\n\n\\* Restrict epmd to loopback only by adding a systemd socket override: set ListenStream= (empty, to clear), then ListenStream=127.0.0.1:4369 and ListenStream=\\[::1\\]:4369 in /etc/systemd/system/epmd.socket.d/override.conf.\n\\* On systemd-managed systems, raise the file descriptor limit and configure automatic restart by adding LimitNOFILE=65536 and Restart=always with a suitable RestartSec in /etc/systemd/system/epmd.service.d/override.conf.\n\\* Restrict network access to TCP port 4369 via firewall rules to trusted hosts only.","affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/erlang/otp","events":[{"introduced":"07b8f441ca711f9812fad9e9115bab3c3aa92f79"},{"fixed":"865d203e4a6a8f44179eced9e1428f9259e4a3bb"}]}],"versions":["patch-base-27","OTP-27.3.4","OTP-27.0","OTP-27.3","OTP-27.3.3","OTP-26.0","OTP-25.0","OTP-27.3.2","OTP-27.2","OTP-27.3.1","OTP-27.1","OTP-27.0-rc3","OTP-27.0-rc2","OTP-27.0-rc1","OTP-24.0","OTP-26.0-rc3","OTP-26.0-rc2","OTP-26.0-rc1","OTP-23.0","OTP-21.0","OTP-25.0-rc3","OTP-25.0-rc2","OTP-25.0-rc1","OTP-22.0","OTP-24.0-rc3","OTP-24.0-rc2","OTP-24.0-rc1","OTP-23.0-rc3","OTP-23.0-rc2","OTP-23.0-rc1","OTP-20.0","OTP-22.0-rc3","OTP-22.0-rc2","OTP-22.0-rc1","OTP-19.0","OTP-21.0-rc2","OTP-18.0","OTP-21.0-rc1","OTP-17.0","OTP-20.0-rc2","OTP-20.0-rc1","OTP-19.0-rc2","OTP-19.0-rc1","OTP-18.0-rc1"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-42792.json","vanir_signatures":[{"deprecated":false,"digest":{"function_hash":"310525855057528063101217745630610969602","length":1917},"id":"EEF-CVE-2026-42792-3e569608","signature_type":"Function","signature_version":"v1","source":"https://github.com/erlang/otp/commit/865d203e4a6a8f44179eced9e1428f9259e4a3bb","target":{"file":"erts/epmd/src/epmd_srv.c","function":"do_read"}},{"deprecated":false,"digest":{"function_hash":"93391892168340247771085395168505802795","length":409},"id":"EEF-CVE-2026-42792-606de8b4","signature_type":"Function","signature_version":"v1","source":"https://github.com/erlang/otp/commit/865d203e4a6a8f44179eced9e1428f9259e4a3bb","target":{"file":"erts/epmd/src/epmd_srv.c","function":"do_accept"}},{"deprecated":false,"digest":{"line_hashes":["238157251032314231486967188355879206108","86184410035617349685376861601664932279","40946427153739319776196253753660958900","61051318659913979963993175574441306207","303349260329761694838462190148736643395","219761322498135725918286544730314218223","146686821301340928619043813619779116451","59933131841513725094244785301980839374","81439414632635711633021290769203132101","294925733372327475393072561666591087259","26485111048758426787724038438679444522","72787819258942913419554890019327627874","190999646518536520587784165358838085546","291588177588217944374030007283233404417","151471799664845060779944634883358307399"],"threshold":0.9},"id":"EEF-CVE-2026-42792-c2d5d3bb","signature_type":"Line","signature_version":"v1","source":"https://github.com/erlang/otp/commit/865d203e4a6a8f44179eced9e1428f9259e4a3bb","target":{"file":"erts/epmd/src/epmd_srv.c"}}],"vanir_signatures_modified":"2026-09-08T08:04:01Z"}}],"references":[{"type":"ADVISORY","url":"https://github.com/erlang/otp/security/advisories/GHSA-h6f3-hx58-xhj6"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-42792.html"},{"type":"WEB","url":"https://www.erlang.org/doc/system/versions.html#order-of-versions"},{"type":"FIX","url":"https://github.com/erlang/otp/commit/865d203e4a6a8f44179eced9e1428f9259e4a3bb"}],"database_specific":{"capec_ids":["CAPEC-227"],"cpe_ids":["cpe:2.3:a:erlang:erlang\\/otp:*:*:*:*:*:*:*:*"],"cwe_ids":["CWE-755","CWE-770"]},"severity":[{"type":"CVSS_V4","score":"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"}],"credits":[{"name":"Ryan Moore","type":"FINDER"},{"name":"John Högberg","type":"REMEDIATION_DEVELOPER"}]}