CVE-2026-23943

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.

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.

La vulnerabilidad de Manejo Inadecuado de Datos Altamente Comprimidos (Bomba de Compresión) en Erlang OTP ssh (módulos ssh_transport) permite la denegación de servicio mediante el agotamiento de recursos. La capa de transporte SSH anuncia la compresión zlib heredada por defecto e infla cargas útiles controladas por el atacante pre-autenticación sin ningún límite de tamaño, lo que permite una DoS fiable por agotamiento de memoria. Dos algoritmos de compresión se ven afectados: * zlib: Se activa inmediatamente después del intercambio de claves, lo que permite ataques no autenticados * zlib@openssh.com: Se activa post-autenticación, lo que permite ataques autenticados Cada paquete SSH puede descomprimir ~255 MB de 256 KB de datos en la red (relación de amplificación de 1029:1). Múltiples paquetes pueden agotar rápidamente la memoria disponible, causando eliminaciones por OOM en entornos con memoria limitada. Esta vulnerabilidad está asociada con los archivos de programa lib/ssh/src/ssh_transport.erl y las rutinas de programa ssh_transport:decompress/2, ssh_transport:handle_packet_part/4. Este problema afecta a OTP desde OTP 17.0 hasta OTP 28.4.1, 27.3.4.9 y 26.2.5.18, lo que corresponde a ssh desde 3.0.1 hasta 5.5.1, 5.2.11.6 y 5.1.4.14.