Siemens kas up to 5.3 kas/libcmds.py ssh_no_host_key_check channel accessible

Summaryinfo

A vulnerability described as problematic has been identified in Siemens kas up to 5.3. Affected by this issue is the function ssh_no_host_key_check of the file kas/libcmds.py. Such manipulation leads to channel accessible. This vulnerability is uniquely identified as CVE-2026-54548. Local access is required to approach this attack. No exploit exists.

Detailsinfo

A vulnerability was found in Siemens kas up to 5.3. It has been rated as problematic. Affected by this issue is the function ssh_no_host_key_check of the file kas/libcmds.py. The manipulation with an unknown input leads to a channel accessible vulnerability. Using CWE to declare the problem leads to CWE-300. The product does not adequately verify the identity of actors at both ends of a communication channel, or does not adequately ensure the integrity of the channel, in a way that allows the channel to be accessed or influenced by an actor that is not an endpoint. Impacted is confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-54548 since 06/15/2026. The exploitation is known to be easy. The attack needs to be approached locally. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 08/26/2026). The MITRE ATT&CK project declares the attack technique as T1557.

Upgrading to version 5.4 eliminates this vulnerability.

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Productinfo

Vendor

• Siemens

Name

• kas

Version

• 5.0
• 5.1
• 5.2
• 5.3

License

• commercial

Website

• Vendor: https://www.siemens.com/
• Product: https://github.com/siemens/kas/

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