CVE-2017-5550 in Linux
Summary
by MITRE
Off-by-one error in the pipe_advance function in lib/iov_iter.c in the Linux kernel before 4.9.5 allows local users to obtain sensitive information from uninitialized heap-memory locations in opportunistic circumstances by reading from a pipe after an incorrect buffer-release decision.
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Analysis
by VulDB Data Team • 11/11/2022
The vulnerability identified as CVE-2017-5550 represents a critical off-by-one error within the Linux kernel's memory management subsystem, specifically in the pipe_advance function located in lib/iov_iter.c. This flaw exists in kernel versions prior to 4.9.5 and constitutes a memory safety issue that can be exploited by local attackers to access uninitialized heap memory. The vulnerability stems from an incorrect buffer release decision that occurs during pipe operations, creating a window where sensitive data may be inadvertently exposed to unauthorized processes. The issue manifests when the kernel incorrectly calculates buffer boundaries during pipe data processing, leading to memory access violations that can result in information disclosure.
The technical implementation of this vulnerability involves the manipulation of pipe buffer management within the kernel's input/output vector iteration framework. When the pipe_advance function processes data movements between pipe buffers, an off-by-one error causes the kernel to release memory incorrectly while still maintaining references to uninitialized memory regions. This memory corruption creates opportunities for local users to perform read operations that can access heap memory locations containing sensitive information from previous allocations. The vulnerability is particularly concerning because it operates in opportunistic circumstances, meaning the exploitation success depends on the specific memory layout and timing conditions present during the attack window. This characteristic makes the vulnerability difficult to predict and defend against, as it requires specific environmental conditions to be present for successful exploitation.
From an operational perspective, this vulnerability presents significant risks to system security and data confidentiality. Local users who can access the system can leverage this flaw to extract potentially sensitive information from kernel memory spaces, including credentials, encryption keys, or other confidential data that may have been stored in previously allocated heap memory regions. The impact extends beyond simple information disclosure as the leaked data could potentially be used to facilitate further attacks or compromise system integrity. The vulnerability affects systems running Linux kernel versions earlier than 4.9.5, making it particularly relevant for organizations that have not yet upgraded their kernel versions. The attack vector requires local access to the system, but this limitation does not diminish the severity of the vulnerability since local privilege escalation or persistent access methods could be used to establish the necessary conditions for exploitation.
The vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and CWE-125, which covers out-of-bounds read errors. From an adversary perspective, this vulnerability could be categorized under ATT&CK technique T1063, which involves the use of kernel modules or kernel exploits to gain elevated privileges. The flaw also represents a memory corruption vulnerability that can be classified under the broader category of memory safety issues. Organizations should prioritize immediate kernel updates to address this vulnerability, as the patch in kernel version 4.9.5 resolves the buffer management logic and corrects the off-by-one error in the pipe_advance function. Additionally, system administrators should implement monitoring for unusual pipe operations and memory access patterns that could indicate exploitation attempts. The vulnerability demonstrates the critical importance of thorough code review and testing of kernel memory management functions, particularly those handling buffer operations and memory allocation decisions.