CVE-2010-3856 in C Library
Summary
by MITRE
ld.so in the GNU C Library (aka glibc or libc6) before 2.11.3, and 2.12.x before 2.12.2, does not properly restrict use of the LD_AUDIT environment variable to reference dynamic shared objects (DSOs) as audit objects, which allows local users to gain privileges by leveraging an unsafe DSO located in a trusted library directory, as demonstrated by libpcprofile.so.
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Analysis
by VulDB Data Team • 06/15/2024
The vulnerability described in CVE-2010-3856 represents a critical privilege escalation flaw within the GNU C Library's dynamic linker component known as ld.so. This issue affects glibc versions prior to 2.11.3 and 2.12.2, creating a pathway for local attackers to elevate their system privileges through manipulation of the LD_AUDIT environment variable. The flaw specifically exploits the improper restriction of audit object references, allowing malicious code execution with elevated privileges. The vulnerability is particularly dangerous because it leverages trusted library directories, making it difficult to detect and prevent through conventional security measures.
The technical implementation of this vulnerability stems from how ld.so processes the LD_AUDIT environment variable, which is designed to specify audit libraries that monitor and log dynamic linking operations. When an application starts with LD_AUDIT set, the dynamic linker loads the specified audit object before the main program begins execution. The flaw occurs because ld.so fails to properly validate the paths of audit objects, allowing attackers to place malicious shared libraries in trusted system directories such as /lib or /usr/lib. This improper validation creates a scenario where the system loads attacker-controlled code with the same privileges as the target application, potentially enabling privilege escalation to root level access. The vulnerability is classified under CWE-276, which deals with improper privilege management, and aligns with ATT&CK technique T1548.001 for privilege escalation through setuid binaries.
The operational impact of CVE-2010-3856 extends beyond simple local privilege escalation, as it can be exploited in various attack scenarios including exploitation of setuid programs, container escape, and system compromise. Attackers can leverage this vulnerability by placing malicious shared libraries in trusted directories and then triggering applications that honor the LD_AUDIT environment variable. The exploitation chain typically involves preparing a malicious DSO in a trusted location, ensuring it has proper permissions, and then executing a setuid program or application that loads the audit library. This vulnerability affects systems running Linux distributions that ship with vulnerable glibc versions, making it widespread across numerous enterprise and consumer environments. The impact is particularly severe when combined with other privilege escalation techniques, as attackers can chain this vulnerability with others to achieve persistent system compromise.
Mitigation strategies for CVE-2010-3856 primarily involve updating glibc to patched versions, specifically glibc 2.11.3 or 2.12.2 and later. System administrators should also implement strict file system permissions and audit trusted library directories for unauthorized modifications. The principle of least privilege should be enforced by removing unnecessary setuid binaries and monitoring applications that utilize LD_AUDIT. Additionally, security configurations should include disabling LD_AUDIT usage in production environments where possible, and implementing file integrity monitoring to detect unauthorized library modifications. Organizations should also consider implementing security modules such as SELinux or AppArmor to provide additional protection layers against such exploitation attempts. The vulnerability serves as a reminder of the critical importance of proper environment variable validation in system libraries and the potential consequences of insufficient input sanitization in core system components.