CVE-2026-23943
MediumCVSS 5.3Exploitation Probability (EPSS)
Low risk47th percentile - higher than 47% of all known CVEs
Summary
Erlang OTP SSH (ssh_transport module) advertises legacy zlib compression by default, allowing a decompression bomb attack pre-authentication. Each SSH packet can decompress ~255 MB from 256 KB of data (1029:1 ratio), leading to memory exhaustion and DoS. Affects OTP from 17.0 before 28.4.1, 27.3.4.9, and 26.2.5.18.
Risk Assessment
An unauthenticated attacker can remotely cause memory exhaustion on the SSH server, leading to denial of service and potential OOM kills.
Recommendation
Update Erlang OTP to version 28.4.1, 27.3.4.9, or 26.2.5.18 (or later). Disable zlib compression in SSH if updating is not possible.
Original NVD description (English source)
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 * [email protected]: 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.