CVE-2017-6188 in munin
Summary
by MITRE
Munin before 2.999.6 has a local file write vulnerability when CGI graphs are enabled. Setting multiple upper_limit GET parameters allows overwriting any file accessible to the www-data user.
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Analysis
by VulDB Data Team • 08/25/2024
The vulnerability identified as CVE-2017-6188 represents a critical local file write flaw in Munin monitoring software versions prior to 2.999.6. This vulnerability specifically manifests when CGI graphs are enabled within the Munin configuration, creating a dangerous attack vector that allows unauthorized file modification. The flaw stems from improper input validation and sanitization within the web interface handling of GET parameters, particularly the upper_limit parameter which is commonly used for defining graph thresholds in monitoring contexts.
The technical implementation of this vulnerability exploits the way Munin processes multiple upper_limit GET parameters through its CGI interface. When these parameters are submitted with maliciously crafted values, the application fails to properly validate or sanitize the input before using it in file operations. This lack of proper input filtering enables an attacker to manipulate the file system operations and overwrite arbitrary files that are accessible to the www-data user account, which typically runs the web server process. The vulnerability essentially allows for arbitrary file write operations within the web server's privileges, potentially leading to complete system compromise.
The operational impact of this vulnerability extends beyond simple file overwrites, as it provides attackers with a means to modify critical system components, configuration files, and potentially inject malicious code into the monitoring infrastructure. Since Munin is commonly used for system monitoring and alerting, compromising this component can provide attackers with persistent access to the monitoring system, enabling them to hide their activities from detection mechanisms. The vulnerability is particularly concerning because it operates within the context of a web application, meaning that exploitation can occur through standard web browser interactions without requiring physical access to the system.
This vulnerability aligns with CWE-939 which addresses Improper Control of Document Access and CWE-22 which covers improper limitation of a pathname to a restricted directory. The attack pattern follows techniques described in MITRE ATT&CK framework under T1059 for command and scripting interpreter and T1078 for valid accounts, as the exploitation leverages existing web server privileges to perform unauthorized file operations. The vulnerability also demonstrates characteristics of privilege escalation through web application exploitation, where a low-privilege web interface access point is used to gain elevated file system access.
Organizations should immediately upgrade to Munin version 2.999.6 or later to remediate this vulnerability, as no effective workarounds exist that can fully mitigate the risk without disabling the vulnerable CGI functionality. Security teams should also implement network segmentation to limit access to Munin web interfaces and monitor for unusual file access patterns or modifications in web server directories. Additionally, regular security assessments should include verification of web application configurations and input validation mechanisms to prevent similar vulnerabilities from being introduced in other monitoring or management interfaces.