CVE-2008-3911 in Linux
Summary
by MITRE
The proc_do_xprt function in net/sunrpc/sysctl.c in the Linux kernel 2.6.26.3 does not check the length of a certain buffer obtained from userspace, which allows local users to overflow a stack-based buffer and have unspecified other impact via a crafted read system call for the /proc/sys/sunrpc/transports file.
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Analysis
by VulDB Data Team • 05/26/2025
The vulnerability identified as CVE-2008-3911 resides within the Linux kernel's sunrpc subsystem, specifically in the proc_do_xprt function located in net/sunrpc/sysctl.c. This flaw represents a classic stack buffer overflow condition that occurs when the kernel fails to validate the length of user-supplied data before processing it. The vulnerability is particularly concerning because it affects a kernel component that handles system control operations, making it accessible through the /proc filesystem interface. The affected kernel version 2.6.26.3 demonstrates that this issue was present in a relatively stable release, indicating that buffer overflow protections were insufficiently implemented in the kernel's rpc transport management code.
The technical implementation of this vulnerability stems from inadequate input validation within the kernel's sysctl interface for the sunrpc subsystem. When a local user executes a crafted read system call against the /proc/sys/sunrpc/transports file, the proc_do_xprt function retrieves data from userspace without performing proper bounds checking on the buffer length. This allows an attacker to supply more data than the allocated stack buffer can accommodate, resulting in a stack overflow condition. The overflow can potentially overwrite adjacent stack memory locations, including return addresses and local variables, which may lead to arbitrary code execution or system instability.
From an operational perspective, this vulnerability presents a significant local privilege escalation vector since it requires only local user access to exploit. The impact extends beyond simple code execution to include potential system compromise and data integrity violations. Attackers could leverage this vulnerability to gain elevated privileges within the kernel space, potentially enabling them to access sensitive system information, modify kernel memory, or establish persistent backdoors. The unspecified other impacts mentioned in the CVE description suggest that the consequences could include system crashes, denial of service conditions, or more sophisticated exploitation techniques that could be chained with other vulnerabilities.
This vulnerability aligns with CWE-121 Stack-based Buffer Overflow, which specifically addresses buffer overflows occurring in stack memory regions where insufficient bounds checking allows data to overwrite adjacent memory locations. The ATT&CK framework categorizes this as a privilege escalation technique through kernel exploitation, specifically mapping to T1068 - Exploitation for Privilege Escalation and T1059 - Command and Scripting Interpreter. The local nature of this exploit means that it fits within the T1548.001 - Abuse Elevation Control Mechanism pattern, as attackers can leverage kernel-level vulnerabilities to bypass standard user access controls. Mitigation strategies should include kernel updates to versions that address this specific buffer overflow, implementation of kernel address space layout randomization, and deployment of kernel hardening techniques such as stack canaries and compile-time protections against buffer overflows.