CVE-2026-23943 — Pre-auth SSH DoS via unbounded zlib inflate

Affected: Erlang OTP

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.

USN-8901-1 — erlang vulnerabilities

Affected: Ubuntu:Pro:14.04:LTS: erlang, Ubuntu:Pro:16.04:LTS: erlang, Ubuntu:Pro:18.04:LTS: erlang, Ubuntu:Pro:20.04:LTS: erlang, Ubuntu:22.04:LTS: erlang, Ubuntu:24.04:LTS: erlang, Ubuntu:26.04:LTS: erlang

Wander Nauta discovered that Erlang incorrectly handled absolute paths when extracting zip archives. An attacker could possibly use this issue to write arbitrary files outside of the intended directory. This issue only affected Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, and Ubuntu 20.04 LTS. (CVE-2025-4748)

It was discovered that the Erlang SFTP server did not properly limit the size of packets. A remote attacker could possibly use this issue to cause Erlang to use excessive resources, leading to a denial of service. This issue only affected Ubuntu 14.04 LTS, Ubuntu 16.04 LTS, and Ubuntu 18.04 LTS. (CVE-2025-26618)

It was discovered that the Erlang SSH server did not properly limit the length of algorithm names in key exchange messages. A remote attacker could possibly use this issue to cause Erlang to use excessive resources, leading to a denial of service. This issue only affected Ubuntu 14.04 LTS, Ubuntu 16.04 LTS, and Ubuntu 18.04 LTS. (CVE-2025-30211)

It was discovered that the Erlang TFTP server incorrectly handled certain file paths. A remote attacker could possibly use this issue to access files outside of the intended directory. (CVE-2026-21620)

It was discovered that the Erlang SFTP server incorrectly validated paths against the configured root directory. An authenticated user could possibly use this issue to access files outside of the root directory. (CVE-2026-23942)

It was discovered that the Erlang SSH server enabled zlib compression by default and did not limit…

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CVE-2026-23943 — Pre-auth SSH DoS via unbounded zlib inflate

USN-8901-1 — erlang vulnerabilities