CVE-2026-54548 — kas: Persistent SSH Host Key Checking Disablement

Affected: siemens kas

kas is a setup tool for bitbake based projects. Prior to 5.4, internal SSH key setup triggered by SSH_PRIVATE_KEY or SSH_PRIVATE_KEY_FILE creates ~/.ssh/config when no user-specific SSH configuration exists and adds a global Host * rule containing StrictHostKeyChecking no. In kas/libcmds.py, ssh_no_host_key_check() runs without checking ctx.managed_env, so the setting persists after kas exits and affects future SSH sessions by the same local user, extending beyond the intended short-lived continuous integration environment. A later SSH connection can therefore accept an attacker-controlled host key without verification, increasing the risk of a man-in-the-middle attack that compromises session confidentiality or integrity. This issue is fixed in version 5.4.

PYSEC-2026-3855 — kas Persistently Disables SSH Host Key Checking

Affected: PyPI: kas

### Summary

kas persistently disables SSH host key checking for the invoking user when internal SSH key setup is triggered via `SSH_PRIVATE_KEY` or `SSH_PRIVATE_KEY_FILE` and no user-specific SSH configuration file exists so far.

When this path is used, kas creates `~/.ssh/config` with a global `Host *` rule containing `StrictHostKeyChecking no`. This was intended to ease the use of kas in short-lived CI environments that lack a pre-configured set of known hosts. In case a local user had no SSH configuration file so far, this approach weakens SSH host authenticity verification beyond the lifetime and scope of the kas command, increasing the risk of successful man-in-the-middle attacks against future SSH connections made by the same user.

### Patches

Such SSH configurations were created since the very first public release. The issue is addressed now by commit <FILLME> which is part of kas version 5.4.

### Workarounds

Since kas 2.6.3, a local user's SSH configuration is only written if it didn't exist before. From that version on, the issue can be avoided by creating an own `~/.ssh/config` prior to calling kas. If kas was already called, `~/.ssh/config` should be inspected and undesired settings created by kas should be removed.

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CVE-2026-54548 — kas: Persistent SSH Host Key Checking Disablement

PYSEC-2026-3855 — kas Persistently Disables SSH Host Key Checking