CVE-2019-18932 in Squid Analysis Report Generator
Summary
by MITRE
log.c in Squid Analysis Report Generator (sarg) through 2.3.11 allows local privilege escalation. By default, it uses a fixed temporary directory /tmp/sarg. As the root user, sarg creates this directory or reuses an existing one in an insecure manner. An attacker can pre-create the directory, and place symlinks in it (after winning a /tmp/sarg/denied.int_unsort race condition). The outcome will be corrupted or newly created files in privileged file system locations.
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Analysis
by VulDB Data Team • 01/22/2020
The vulnerability identified as CVE-2019-18932 resides within the Squid Analysis Report Generator (sarg) software version 2.3.11 and earlier, presenting a critical local privilege escalation vector. This flaw manifests through improper handling of temporary directories during the software's operation, specifically in the log.c component where the application defaults to utilizing a fixed temporary directory located at /tmp/sarg. The issue stems from the insecure creation and reuse of this temporary directory by the root user during sarg's execution, creating a predictable attack surface that adversaries can exploit to gain elevated privileges.
The technical mechanism of exploitation involves a race condition scenario that occurs during the initialization phase of sarg's operation. When sarg runs as root and attempts to create or access the /tmp/sarg directory, it does so without proper security checks that would prevent malicious interference. An attacker can pre-position themselves in this temporal window by creating the /tmp/sarg directory structure beforehand, then placing symbolic links within it that point to sensitive system locations. This creates a scenario where subsequent file operations performed by sarg will inadvertently write to privileged locations, effectively allowing the attacker to modify files that should only be accessible to the root user. The vulnerability operates under the CWE-367 principle of Time-of-Check to Time-of-Use (TOCTOU) flaws, where the security check occurs at a different time than the actual operation.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it fundamentally compromises the integrity of the system's privilege model. When an attacker successfully exploits this vulnerability, they can manipulate critical system files, potentially leading to persistent backdoors, system compromise, or complete control over the affected system. The attack requires local access to the system but provides a path to root privileges, making it particularly dangerous in environments where local users might have limited access but could leverage this vulnerability to escalate their privileges. The vulnerability aligns with ATT&CK technique T1068, which describes the use of local privilege escalation techniques, and specifically targets the privilege escalation sub-technique T1068.001. The exploitation process can be automated and does not require sophisticated tools, making it accessible to attackers with basic system knowledge.
Mitigation strategies for CVE-2019-18932 must address both the immediate software vulnerability and broader system security practices. The primary remediation involves upgrading to a patched version of sarg that properly handles temporary directory creation and avoids the insecure use of fixed temporary paths. Organizations should also implement proper file system permissions and access controls, ensuring that temporary directories are created with appropriate security contexts and that symbolic link protections are enforced. System administrators should consider implementing additional security measures such as SELinux policies or AppArmor profiles to limit the impact of such vulnerabilities. The vulnerability demonstrates the importance of secure coding practices in system administration tools and highlights the need for proper privilege separation and secure temporary file handling. Regular security audits and vulnerability assessments should include checks for similar insecure temporary file handling patterns across all system utilities and applications, particularly those that run with elevated privileges.