CVE-2026-55601
Description
A flaw was found in MultiTail. When using the execute-on-match feature, MultiTail fails to properly sanitize matched log data before passing it to the system shell for command execution. An attacker capable of influencing the contents of monitored input can exploit this issue by injecting shell metacharacters, resulting in arbitrary command execution with the privileges of the user running MultiTail.
Statement
This vulnerability is rated as having Important impact because an attacker capable of injecting content into monitored log streams can achieve arbitrary shell execution under the privileges of the active session. Exploitation requires non-default execute-on-match options or configuration directives to be invoked against inputs that process untrusted data. Furthermore, multitail is not part of core Red Hat Enterprise Linux and is only distributed through EPEL and Fedora community channels.
Mitigation
Avoid using the `-ex` or `-eX` command-line options to execute commands on matching regular expressions when inspecting log files or streams that untrusted users can write to. Additionally, verify that configuration files such as `/etc/multitail.conf` and `~/.multitailrc` do not define automated command execution actions for untrusted sources.
Caveats: Disabling or avoiding these parameters prevents automated script execution when log patterns match.
Understanding the Weakness (CWE)
Confidentiality,Integrity,Availability,Non-Repudiation
Technical Impact: Execute Unauthorized Code or Commands; DoS: Crash, Exit, or Restart; Read Files or Directories; Modify Files or Directories; Read Application Data; Modify Application Data; Hide Activities
Attackers could execute unauthorized operating system commands, which could then be used to disable the product, or read and modify data for which the attacker does not have permissions to access directly. Since the targeted application is directly executing the commands instead of the attacker, any malicious activities may appear to come from the application or the application's owner.
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