CVE-2026-42792: epmd permanent DoS via EMFILE on accept(2) in erts

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-27 · updated 2026-10-24
Weakness: CWE-755

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.

Affected products

Erlang OTP: from 17.0 before 27.3.4; from 28.0 before 28.5.0.4; from 29.0 before 29.0.4 — fixed in 27.3.4, 28.5.0.4, 29.0.4
Erlang Erts: from 6.0 before 15.2.7.11; from 16.0 before 16.4.0.4; from 17.0 before 17.0.4 — fixed in 15.2.7.11, 16.4.0.4, 17.0.4

How to fix

Upgrade to a fixed version: Erlang OTP 27.3.4, 28.5.0.4, 29.0.4; Erlang Erts 15.2.7.11, 16.4.0.4, 17.0.4. Check the vendor advisory for mitigations.

References

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