---
id: CVE-2026-23943
title: >-
  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 defaul…
summary: >-
  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 defaul…
severity: medium
cvss: 5.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'
cwe:
  - CWE-409
vendor: erlang
product: erlang/otp
affected:
  - 'erlang/otp >= 17.0, < 26.2.5.18'
  - 'erlang/otp >= 27.0, < 27.3.4.9'
  - 'erlang/otp >= 28.0, < 28.4.1'
  - 'erlang/ssh >= 3.0.1, < 5.1.4.14'
  - 'erlang/ssh >= 5.2, < 5.2.11.6'
  - 'erlang/ssh >= 5.5, <= 5.5.1'
patched:
  - erlang/otp 28.4.1
  - erlang/ssh 5.2.11.6
published: '2026-03-13'
updated: '2026-07-24'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-23943'
references:
  - url: 'https://cna.erlef.org/cves/CVE-2026-23943.html'
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/erlang/otp/commit/0c1c04b191f6ab940e8fcfabce39eb5a8a6440a4
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/erlang/otp/commit/43a87b949bdff12d629a8c34146711d9da93b1b1
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/erlang/otp/commit/93073c3bd338c60cd2bae715ce6a1d4ffc1a8fd3
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: 'https://github.com/erlang/otp/security/advisories/GHSA-c836-qprm-jw9r'
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: 'https://osv.dev/vulnerability/EEF-CVE-2026-23943'
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: 'https://www.erlang.org/doc/system/versions.html#order-of-versions'
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
tags:
  - nvd
epss: 0.00644
epssPercentile: 0.49514
ingestedAt: '2026-07-24T15:30:58.218Z'
---

## Overview

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.

## Affected

- `erlang/otp >= 17.0, < 26.2.5.18`
- `erlang/otp >= 27.0, < 27.3.4.9`
- `erlang/otp >= 28.0, < 28.4.1`
- `erlang/ssh >= 3.0.1, < 5.1.4.14`
- `erlang/ssh >= 5.2, < 5.2.11.6`
- `erlang/ssh >= 5.5, <= 5.5.1`

## Remediation

Upgrade past the affected range:

- `erlang/otp 28.4.1`
- `erlang/ssh 5.2.11.6`