CVE-2026-68956

Publication date 22 September 2026

Last updated 8 October 2026

Ubuntu priority

Medium

Why this priority?

Description

Allocation of Resources Without Limits or Throttling vulnerability in Erlang/OTP ssh allows an authenticated remote attacker to exhaust node memory by repeatedly opening session channels that are never assigned a handler. The "session" clause of ssh_connection:handle_msg/4 checks only minimal_remote_max_packet_size before calling setup_session/5, which unconditionally builds a #channel{} record and stores it in the ETS channel cache. The max_channels daemon option is consulted only by ssh_channel_sup:max_num_channels_not_exceeded/2, which counts supervisor children, so a channel that never gets a shell, exec, or subsystem handler is invisible to the limit and setting the option to a finite value does not mitigate the attack. RFC 4254 section 5.1 permits many session channels per connection, and each record costs only a few hundred bytes, so a single authenticated connection can accumulate channels until the node runs out of memory and the emulator terminates, affecting every application on it. No file contents, credentials, or write access are obtainable. This issue affects OTP from OTP 18.1.2 before OTP 27.3.4.18, OTP 28.5.0.7, and OTP 29.1.1, corresponding to ssh from 4.1.1 before 5.2.11.13, 5.5.2.6, and 6.0.6. Whether OTP before OTP 18.1.2, corresponding to ssh before 4.1.1, is affected is unknown.

Status

Package Ubuntu Release Status
erlang 26.04 LTS resolute
Fixed 1:27.3.4.6+dfsg-1ubuntu0.2
24.04 LTS noble
Fixed 1:25.3.2.8+dfsg-1ubuntu4.8
22.04 LTS jammy
Fixed 1:24.2.1+dfsg-1ubuntu0.8
20.04 LTS focal
Fixed 1:22.2.7+dfsg-1ubuntu0.5+esm3
18.04 LTS bionic
Fixed 1:20.2.2+dfsg-1ubuntu2+esm4
16.04 LTS xenial
Fixed 1:18.3-dfsg-1ubuntu3.1+esm4
14.04 LTS trusty Ignored changes too intrusive

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Severity score breakdown

CVSS version: CVSS v4.0

Base score 7.1 · High

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

References

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