Riskcovery

CVE-2026-42792

epmd permanent DoS via EMFILE on accept(2) in erts

State
Published
Severity
6.3 Medium
Published
Jul 27, 2026
Updated
Jul 28, 2026
Reserved
Apr 29, 2026

Read the record on cve.org

Description

Improper 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.

The 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.

On 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.

This issue affects OTP from OTP 17.0 before OTP 29.0.4, OTP 28.5.0.4 and OTP 27.3.4.15.

Scores

CVSSScoreVectorSource
4.06.3 MediumCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:NEEF

Weaknesses

  • CWE-755 Improper Handling of Exceptional Conditions
  • CWE-770 Allocation of Resources Without Limits or Throttling

Affected Products

ProductVersions
OTPErlang
  • 6.0 and laterAffectedfrom 17.0.4Not affectedfrom 16.4.0.4Not affectedfrom 15.2.7.11Not affected
OTPErlang
  • 17.0 and laterAffectedfrom 29.0.4Not affectedfrom 28.5.0.4Not affectedfrom 27.3.4.15Not affected
  • 07b8f441ca711f9812fad9e9115bab3c3aa92f79 to before 865d203e4a6a8f44179eced9e1428f9259e4a3bbAffected

References

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