6.9

CVE-2026-23943

Pre-auth SSH DoS via unbounded zlib inflate

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 until OTP 28.4.1, 27.3.4.9 and 26.2.5.18 corresponding to ssh from 3.0.1 until 5.5.1, 5.2.11.6 and 5.1.4.14.
Daten sind bereitgestellt durch National Vulnerability Database (NVD)
Erlang ≫ Erlang/otp Version >= 17.0 < 26.2.5.18
Erlang ≫ Erlang/otp Version >= 27.0 < 27.3.4.9
Erlang ≫ Erlang/otp Version >= 28.0 < 28.4.1
Erlang ≫ Erlang/ssh Version >= 3.0.1 < 5.1.4.14
Erlang ≫ Erlang/ssh Version >= 5.2 < 5.2.11.6
Erlang ≫ Erlang/ssh Version >= 5.5 <= 5.5.1
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EPSS Metriken
Typ Quelle Score Percentile
EPSS FIRST.org 0.64% 0.46
CVSS Metriken
Quelle Base Score Exploit Score Impact Score Vector String
nvd@nist.gov 5.3 3.9 1.4
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
6b3ad84c-e1a6-4bf7-a703-f496b71e49db 6.9 0 0
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CWE-409 Improper Handling of Highly Compressed Data (Data Amplification)

The product does not handle or incorrectly handles a compressed input with a very high compression ratio that produces a large output.

https://www.erlang.org/doc/system/versions.html#order-of-versions
Product
https://github.com/erlang/otp/security/advisories/GHSA-c836-qprm-jw9r
Vendor Advisory
https://github.com/erlang/otp/commit/43a87b949bdff12d629a8c34146711d9da93b1b1
Patch
https://github.com/erlang/otp/commit/93073c3bd338c60cd2bae715ce6a1d4ffc1a8fd3
Patch
https://github.com/erlang/otp/commit/0c1c04b191f6ab940e8fcfabce39eb5a8a6440a4
Patch
https://cna.erlef.org/cves/CVE-2026-23943.html
Vendor Advisory
https://osv.dev/vulnerability/EEF-CVE-2026-23943
Third Party Advisory