CVE-2018-18925 in Gogs
Summary
by MITRE
Gogs 0.11.66 allows remote code execution because it does not properly validate session IDs, as demonstrated by a ".." session-file forgery in the file session provider in file.go. This is related to session ID handling in the go-macaron/session code for Macaron.
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Analysis
by VulDB Data Team • 06/04/2023
The vulnerability CVE-2018-18925 represents a critical remote code execution flaw in Gogs version 0.11.66 that stems from inadequate session ID validation mechanisms. This vulnerability specifically affects the file session provider implementation within Gogs' session management system, where the application fails to properly validate session identifiers, creating a path for malicious actors to exploit. The flaw manifests through a directory traversal attack pattern involving double dot sequences ".." that can be embedded within session file names, allowing attackers to manipulate session storage locations and potentially execute arbitrary code on the affected system.
The technical root cause of this vulnerability lies in the improper handling of session identifiers within the go-macaron/session library that Gogs utilizes for its session management functionality. When session IDs are processed, the system does not adequately sanitize or validate the input, particularly when dealing with file-based session storage. This validation failure creates a condition where attacker-controlled session IDs can contain malicious path traversal sequences that bypass normal file system access controls. The vulnerability is classified under CWE-22 as a directory traversal weakness, where insufficient input validation allows attackers to access files outside the intended directory structure. The specific implementation flaw occurs in the file.go component of the session provider, where session file names are constructed without proper sanitization of the session identifier.
The operational impact of this vulnerability is severe and far-reaching for organizations utilizing affected Gogs installations. Remote attackers can leverage this flaw to execute arbitrary code with the privileges of the Gogs service account, potentially leading to complete system compromise. The vulnerability enables attackers to manipulate session storage files, potentially gaining access to sensitive user data, modifying session information to escalate privileges, or even injecting malicious code into the application's runtime environment. This type of vulnerability directly maps to ATT&CK technique T1059.001 for command and script injection, as the remote code execution capability allows attackers to execute arbitrary commands on the target system. Organizations running Gogs instances without proper patches or mitigations face significant risk of unauthorized access, data breaches, and potential lateral movement within their network infrastructure.
Mitigation strategies for CVE-2018-18925 should prioritize immediate patching of affected Gogs installations to version 0.11.67 or later, which contains the necessary fixes for session ID validation. Administrators should also implement additional security controls including network segmentation to limit access to Gogs instances, enabling secure session storage configurations that prevent file system traversal attacks, and monitoring for unusual session file access patterns. Organizations should consider implementing web application firewalls to detect and block malicious session ID patterns, while also conducting thorough security assessments of their session management implementations. The vulnerability highlights the importance of proper input validation and sanitization in session handling components, emphasizing the need for robust security practices in the development and maintenance of web applications. Regular security updates and vulnerability assessments should be implemented to prevent similar issues from arising in other components of the application stack, particularly given the widespread use of the Macaron framework and its session management libraries.