CVE-2011-1658 in C Library
Summary
by MITRE
ld.so in the GNU C Library (aka glibc or libc6) 2.13 and earlier expands the $ORIGIN dynamic string token when RPATH is composed entirely of this token, which might allow local users to gain privileges by creating a hard link in an arbitrary directory to a (1) setuid or (2) setgid program with this RPATH value, and then executing the program with a crafted value for the LD_PRELOAD environment variable, a different vulnerability than CVE-2010-3847 and CVE-2011-0536. NOTE: it is not expected that any standard operating-system distribution would ship an applicable setuid or setgid program.
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Analysis
by VulDB Data Team • 10/21/2021
The vulnerability described in CVE-2011-1658 resides within the dynamic linker component of the GNU C Library known as ld.so, which is a critical element in Unix-like operating systems responsible for loading shared libraries at runtime. This flaw specifically affects glibc versions 2.13 and earlier, where the dynamic string token $ORIGIN is improperly expanded when used in RPATH (run-time search path) configurations. The $ORIGIN token is designed to represent the directory containing the shared object being loaded, serving as a mechanism for relative path resolution in dynamic linking. When RPATH is constructed entirely from this token, the vulnerability manifests in a manner that could potentially be exploited for privilege escalation.
The technical exploitation of this vulnerability requires a specific combination of conditions that create a path traversal scenario. An attacker must first establish a hard link to a setuid or setgid program that has an RPATH value composed entirely of the $ORIGIN token. This setup allows the attacker to manipulate the library loading process by crafting a value for the LD_PRELOAD environment variable. The flaw occurs because ld.so does not properly validate or sanitize the expansion of $ORIGIN when it constitutes the entire RPATH specification, potentially leading to the loading of attacker-controlled libraries from unexpected locations. This behavior creates a vector where the dynamic linker's path resolution logic can be subverted to load malicious code instead of legitimate system libraries. The vulnerability is categorized under CWE-22 as Improper Limitation of a Pathname to a Known Good Path, and it aligns with ATT&CK technique T1068 which covers Exploitation for Privilege Escalation through dynamic linkers.
The operational impact of this vulnerability extends beyond typical local privilege escalation scenarios due to its reliance on specific program configurations and environmental conditions. While the advisory notes that standard distributions do not ship with setuid/setgid programs that would be vulnerable, the flaw remains significant in environments where such programs are present or custom applications are deployed. The exploitation requires careful preparation involving hard link creation and environment variable manipulation, making it less trivial than some other privilege escalation vectors. However, the potential for local users to gain elevated privileges through this mechanism represents a serious security concern, particularly in multi-user systems or environments where users have the ability to create hard links. The vulnerability demonstrates how seemingly benign dynamic linking features can create security risks when combined with improper input validation and path resolution logic. This issue is particularly concerning in contexts where privilege separation is critical, as it could allow unprivileged users to execute code with elevated permissions through carefully crafted library loading sequences. The flaw essentially undermines the expected security boundaries established by setuid/setgid programs, creating an attack surface that could be leveraged in targeted environments where such programs exist.