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 26.2.5.18, OTP 27.3.4.9, and OTP 28.4.1, corresponding to ssh from 3.0.1 before 5.1.4.14, 5.2.11.6, and 5.5.1.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Erlang | OTP | 17.0, 3.0.1 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | erlang | 1:27.3.4.9+dfsg-1 | — |
| Debian 13 | erlang | 1:27.3.4.1+dfsg-1+deb13u2 | — |
| Debian 12 | erlang | 1:25.2.3+dfsg-1+deb12u4 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.04 LTS | erlang | 1:27.3.4.6+dfsg-1ubuntu0.2 | USN-8901-1 |
| Ubuntu 25.10 | erlang | No fix yet | — |
| Ubuntu 24.04 LTS | erlang | 1:25.3.2.8+dfsg-1ubuntu4.8 | USN-8901-1 |
| Ubuntu 22.04 LTS | erlang | 1:24.2.1+dfsg-1ubuntu0.8 | USN-8901-1 |
Show 4 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 20.04 LTS | erlang | 1:22.2.7+dfsg-1ubuntu0.5+esm3 | USN-8901-1 |
| Ubuntu Pro 18.04 LTS | erlang | 1:20.2.2+dfsg-1ubuntu2+esm4 | USN-8901-1 |
| Ubuntu Pro 16.04 LTS | erlang | 1:18.3-dfsg-1ubuntu3.1+esm4 | USN-8901-1 |
| Ubuntu Pro 14.04 LTS | erlang | 1:16.b.3-dfsg-1ubuntu2.2+esm3 | USN-8901-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | erlang27 | 27.1.3-2.1 | openSUSE-SU-2026:10947-1 |
| openSUSE Leap 16.0 | erlang | 27.1.3-160000.4.1 | openSUSE-SU-2026:20607-1 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | erlang | 26.2.5.18-1 | — |
Advisories 4
- USN-8901-1 erlang vulnerabilities Ubuntu Security Notices (USN) · Oct 8, 2026
- WID-SEC-2026-0721 Erlang/OTP: Mehrere Schwachstellen BSI CERT-Bund (WID) · Sep 28, 2026
- openSUSE-SU-2026:10947-1 erlang27-27.1.3-2.1 on GA media SUSE / openSUSE Security Updates · Jun 4, 2026
- openSUSE-SU-2026:20607-1 Security update for erlang SUSE / openSUSE Security Updates · Apr 24, 2026
References
- Pre-auth SSH DoS via unbounded zlib inflate vendor-advisory related
- EEF CNA record for CVE-2026-23943 related
- OSV record EEF-CVE-2026-23943 related
- Erlang/OTP version ordering
- Introducing commit 07b8f44 in erlang/otp related
- Fix commit 0c1c04b in erlang/otp patch
- Fix commit 93073c3 in erlang/otp patch
- Fix commit 43a87b9 in erlang/otp patch