CVE-2026-59845 — Libssh: libssh: denial of service via unchecked proxycommand fork() failure

Affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat Hardened Images

A flaw was found in libssh. When ProxyCommand is used, an unchecked fork() failure can be stored as process ID -1; during cleanup, signals may then be sent across the caller's accessible process tree, leading to local denial of service.

USN-8699-1 — libssh vulnerabilities

Affected: Ubuntu:22.04:LTS: libssh, Ubuntu:24.04:LTS: libssh, Ubuntu:26.04:LTS: libssh

It was discovered that libssh had a stack buffer overflow in its SFTP server when constructing directory listing entries for long filenames. An attacker could possibly use this issue to cause libssh to crash or execute arbitrary code. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-15370)

It was discovered that libssh did not correctly handle SSH channel open messages advertising a zero maximum packet size. An authenticated remote attacker could possibly use this issue to cause libssh to consume excessive CPU resources, leading to a denial of service. (CVE-2026-59843)

It was discovered that libssh did not correctly limit SFTP read request lengths in its server implementation. An authenticated remote attacker could possibly use this issue to cause libssh to allocate excessive memory, leading to a denial of service. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-59844)

It was discovered that libssh did not correctly handle ProxyCommand fork() failures. A local attacker could possibly use this issue to cause a denial of service. (CVE-2026-59845)

It was discovered that libssh did not correctly sanitize shell metacharacters when expanding usernames in ProxyCommand strings. An attacker could possibly use this issue to obtain sensitive information. (CVE-2026-59846)

It was discovered that libssh had incorrect AES-GCM tag verification when built with the OpenSSL backend. A machine-in-the-middle attacker could possibly use this issue to modify encrypted traffic without…

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CVE-2026-59845 — Libssh: libssh: denial of service via unchecked proxycommand fork() failure

USN-8699-1 — libssh vulnerabilities