CVE-2013-1979 in Linux
Summary
by MITRE
The scm_set_cred function in include/net/scm.h in the Linux kernel before 3.8.11 uses incorrect uid and gid values during credentials passing, which allows local users to gain privileges via a crafted application.
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Analysis
by VulDB Data Team • 05/10/2021
The vulnerability identified as CVE-2013-1979 resides within the Linux kernel's implementation of socket credentials handling, specifically in the scm_set_cred function located in include/net/scm.h. This flaw represents a critical privilege escalation vulnerability that affects Linux kernel versions prior to 3.8.11, where the kernel fails to properly validate or process user and group identifiers during the transmission of socket credentials between processes. The issue manifests when applications attempt to pass credentials through Unix domain sockets using the SCM_CREDENTIALS option, which is a legitimate kernel feature for authenticating process ownership in inter-process communication scenarios.
The technical root cause of this vulnerability stems from improper handling of uid and gid values within the scm_set_cred function, which operates under the assumption that credentials passed through socket control messages are trustworthy. When a local user crafts a malicious application that sends specially constructed socket control messages with malformed uid and gid values, the kernel's credential validation mechanism fails to properly sanitize these values before they are processed. This misimplementation creates a situation where unprivileged users can manipulate the credential passing mechanism to potentially elevate their privileges within the system. The vulnerability specifically affects the kernel's ability to correctly map and validate user identifiers during the credential passing process, leading to potential privilege escalation attacks.
From an operational perspective, this vulnerability presents a significant security risk for local users who can exploit it to gain elevated privileges within the Linux environment. The attack vector requires local system access and involves crafting a malicious application that leverages the socket credentials passing mechanism. Once exploited, attackers can potentially escalate their privileges from standard user level to root or administrative privileges, depending on the system configuration and the specific credentials being manipulated. The impact extends beyond simple privilege escalation as it can enable attackers to bypass various security controls that rely on proper credential validation, including access control lists, file permissions, and process isolation mechanisms. This vulnerability is particularly dangerous in multi-user environments where local users might attempt to exploit it to gain unauthorized access to system resources or escalate their privileges to gain full administrative control.
The security implications of CVE-2013-1979 align with CWE-284, which addresses improper access control, and can be mapped to ATT&CK technique T1068, which covers privilege escalation through local exploits. The vulnerability demonstrates how kernel-level credential handling flaws can be exploited to bypass fundamental security boundaries. Mitigation strategies should include immediate patching of affected kernel versions to 3.8.11 or later, where the issue has been resolved through proper credential validation mechanisms. System administrators should also implement monitoring for suspicious socket credential usage patterns and consider restricting access to Unix domain socket functionality where possible. Additionally, the vulnerability highlights the importance of thorough input validation in kernel space, as the flaw could have been prevented through proper bounds checking and credential sanitization. The fix implemented in kernel version 3.8.11 addresses the core issue by ensuring that uid and gid values are properly validated and sanitized before being accepted as valid credentials, thereby preventing the privilege escalation attack vector.