CVE-2017-17852 in Linux
Summary
by MITRE • 01/25/2023
kernel/bpf/verifier.c in the Linux kernel through 4.14.8 allows local users to cause a denial of service (memory corruption) or possibly have unspecified other impact by leveraging mishandling of 32-bit ALU ops.
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Analysis
by VulDB Data Team • 01/25/2023
The vulnerability identified as CVE-2017-17852 resides within the Linux kernel's eBPF (extended Berkeley Packet Filter) verifier component, specifically in the kernel/bpf/verifier.c file. This flaw affects Linux kernel versions through 4.14.8 and represents a critical security issue that can be exploited by local attackers to cause system instability. The vulnerability stems from improper handling of 32-bit Arithmetic Logic Unit operations within the eBPF verification process, creating a pathway for memory corruption that can lead to system crashes or more severe consequences.
The technical root cause of this vulnerability lies in how the kernel's eBPF verifier processes 32-bit arithmetic operations during program validation. When eBPF programs are loaded into the kernel, the verifier performs extensive checks to ensure program safety and prevent malicious code execution. However, the flaw occurs during the validation of 32-bit ALU operations where the verifier fails to properly account for certain edge cases in operand handling. This improper validation allows an attacker to craft malicious eBPF programs that can manipulate the verifier's internal state, leading to memory corruption. The issue manifests when the verifier incorrectly calculates or interprets 32-bit arithmetic results, causing it to follow invalid execution paths that ultimately result in memory corruption.
From an operational perspective, this vulnerability presents significant risks to systems running affected kernel versions. Local attackers with access to the system can leverage this flaw to either cause a denial of service through system crashes or potentially achieve more severe impacts including privilege escalation. The attack vector is particularly concerning because it requires only local access and does not need network connectivity or specialized privileges beyond what a regular user might already possess. The memory corruption can lead to unpredictable system behavior, kernel panics, or even allow an attacker to execute arbitrary code with kernel privileges, depending on the specific exploitation scenario. This makes the vulnerability particularly dangerous in multi-tenant environments or systems where local user access cannot be strictly controlled.
The impact of this vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and can be categorized under ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation'. Organizations should implement immediate mitigations including kernel updates to versions that contain patches for this vulnerability, typically kernel versions 4.14.9 and later. System administrators should also consider implementing eBPF program restrictions or disabling eBPF functionality entirely if it is not essential for operations. Additional monitoring should be deployed to detect unusual eBPF program loading activities, as this vulnerability specifically targets the eBPF verifier's program validation logic rather than runtime execution, making detection during the loading phase crucial for prevention. The vulnerability demonstrates the critical importance of thorough validation in kernel-level components and highlights the potential for seemingly benign arithmetic operations to create serious security implications when not properly handled in complex verification systems.