Linuxfabrik linuxfabrik-lib/Linuxfabrik Monitoring Plugins Shell Execution restic-check lib.shell.shell_exec repo os command injection

Summaryinfo

A vulnerability described as very critical has been identified in Linuxfabrik linuxfabrik-lib and Linuxfabrik Monitoring Plugins. Impacted is the function lib.shell.shell_exec of the file check-plugins/restic-check/restic-check of the component Shell Execution. Such manipulation of the argument repo leads to os command injection. This vulnerability is uniquely identified as CVE-2026-55426. Local access is required to approach this attack. No exploit exists.

Detailsinfo

A vulnerability was found in Linuxfabrik linuxfabrik-lib and Linuxfabrik Monitoring Plugins (unknown version). It has been rated as very critical. Affected by this issue is the function lib.shell.shell_exec of the file check-plugins/restic-check/restic-check of the component Shell Execution. The manipulation of the argument repo with an unknown input leads to a os command injection vulnerability. Using CWE to declare the problem leads to CWE-78. The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component. Impacted is confidentiality, integrity, and availability. CVE summarizes:

linuxfabrik-lib provides Python modules for database access, caching, shell execution, and API integrations, and Linuxfabrik Monitoring Plugins uses those modules to run external monitoring commands. From the earliest affected releases until linuxfabrik-lib 5.0.0 and Linuxfabrik Monitoring Plugins 6.0.0, check plugins embedded user-controlled values in command strings passed to lib.shell.shell_exec(), which split strings at pipe characters and executed the resulting commands. In check-plugins/restic-check/restic-check, the --repo parameter could inject a pipe-delimited command into a constructed restic invocation, and sudo-authorized execution allowed a compromised nagios or icinga account to run that command as root. The shared library also accepted command strings and a shell parameter, while numerous plugins constructed external commands from attacker-influenced arguments. The fixes require argv lists, always use shell=False, remove pipe splitting, and reject option-like positional values through lib.shell.safe_cli_value(). These issues are fixed in linuxfabrik-lib 5.0.0 and Linuxfabrik Monitoring Plugins 6.0.0.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-55426 since 06/16/2026. The exploitation is known to be easy. The attack needs to be approached locally. Additional levels of successful authentication are required for exploitation. 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 08/18/2026). The MITRE ATT&CK project declares the attack technique as T1202.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Vendor

• Linuxfabrik

Name

• linuxfabrik-lib
• Linuxfabrik Monitoring Plugins

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