Bug 2507551 (CVE-2026-42792)

Summary: CVE-2026-42792 erlang-otp: epmd: Erlang OTP epmd: Remote Denial of Service via connection exhaustion
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in Erlang OTP's Erlang Port Mapper Daemon (epmd). An unauthenticated remote attacker can exploit an improper handling of exceptional conditions in the do_accept function. By exhausting connection slots through holding numerous TCP connections open and periodically sending data, the attacker can force epmd to terminate, leading to a permanent Denial of Service (DoS). This can further impact system stability on certain Linux distributions by causing related services to fail permanently.
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Description OSIDB Bzimport 2026-07-27 16:01:51 UTC 
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 27.3.4.15, 28.5.0.4, and 29.0.4.