Can you explain this vulnerability to me?

CVE-2025-67903 is a signature verification bypass vulnerability in the Mender Client software versions 5.0.0 to 5.0.3. It allows an attacker to add malicious files to a Mender Artifact without triggering signature or checksum verification failures in the client.

This happens because the malicious files are not listed with a checksum in the update manifest, which bypasses the security checks normally performed by the client.

However, for this vulnerability to be exploited, the vulnerable Mender Client must be used with a custom update module that installs or executes these additional files, and a custom update server that does not validate artifacts using mender-artifact.

The default update modules and Mender Server are not vulnerable, which reduces the risk of widespread exploitation.

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How can this vulnerability impact me? :

If exploited, this vulnerability could allow an attacker to introduce malicious files into a device managed by the vulnerable Mender Client without detection by signature or checksum verification.

This could potentially lead to unauthorized code execution or compromise of the device if the malicious files are installed or executed via a custom update module and server.

However, the impact is limited because exploitation requires specific conditions: a vulnerable client, a custom update module, and a custom update server that does not perform proper artifact validation.

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How can this vulnerability be detected on my network or system? Can you suggest some commands?

This vulnerability affects Mender Client versions 5.0.0 to 5.0.3 and involves a cryptographic signature verification bypass. Detection involves identifying if your system is running a vulnerable Mender Client version.

You can check the installed Mender Client version on your system using commands like:

• mender --version
• dpkg -l | grep mender-client (on Debian-based systems)
• rpm -qa | grep mender-client (on RPM-based systems)

If the version is between 5.0.0 and 5.0.3, your system is vulnerable to this signature verification bypass.

Additionally, since exploitation requires a custom update module and server, monitoring for unusual update artifacts or custom update modules could help detect attempts to exploit this vulnerability.

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What immediate steps should I take to mitigate this vulnerability?

The primary mitigation step is to upgrade the Mender Client to a fixed version. Specifically, upgrade to version 5.0.4, 6.0.0, or later.

Since the vulnerability requires a custom update module and server to be exploited, ensure that your update infrastructure uses the default Mender Server and update modules, which are not vulnerable.

Review and restrict access to your update servers and modules to prevent unauthorized custom update modules or servers from being used.

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How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:

The vulnerability in Mender Client allows a cryptographic signature verification bypass, which could potentially enable unauthorized or malicious files to be added to device updates without detection.

Such a security weakness may impact compliance with standards and regulations like GDPR and HIPAA, which require maintaining the integrity and security of systems processing sensitive data.

However, the vulnerability's exploitation requires specific conditions, including a custom update module and server, and the default Mender Server and update modules are not vulnerable, which limits the risk.

To mitigate compliance risks, affected users are advised to upgrade to fixed versions of the Mender Client.

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