CVE-2026-23943

Publication date 13 March 2026

Last updated 8 October 2026

Ubuntu priority

Medium

Why this priority?

Cvss 3 Severity Score

5.3 · Medium

Score breakdown

Description

Improper Handling of Highly Compressed Data (Compression Bomb) vulnerability in Erlang OTP ssh (ssh_transport modules) allows Denial of Service via Resource Depletion. The SSH transport layer advertises legacy zlib compression by default and inflates attacker-controlled payloads pre-authentication without any size limit, enabling reliable memory exhaustion DoS. Two compression algorithms are affected: * zlib: Activates immediately after key exchange, enabling unauthenticated attacks * zlib@openssh.com: Activates post-authentication, enabling authenticated attacks Each SSH packet can decompress ~255 MB from 256 KB of wire data (1029:1 amplification ratio). Multiple packets can rapidly exhaust available memory, causing OOM kills in memory-constrained environments. This vulnerability is associated with program files lib/ssh/src/ssh_transport.erl and program routines ssh_transport:decompress/2, ssh_transport:handle_packet_part/4. This issue affects OTP from OTP 17.0 before OTP 28.4.1, OTP 27.3.4.9 and OTP 26.2.5.18, corresponding to ssh from 3.0.1 before 5.5.1, 5.2.11.6 and 5.1.4.14.

Status

Package Ubuntu Release Status
erlang 26.04 LTS resolute
Fixed 1:27.3.4.6+dfsg-1ubuntu0.2
25.10 questing Ignored end of life, was needs-triage
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
Fixed 1:16.b.3-dfsg-1ubuntu2.2+esm3

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Severity score breakdown

CVSS version:

Base score 6.9 · Medium

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

Base score 5.3 · Medium

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

References

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