CVE-2017-17857 in Linux
Summary
by MITRE
The check_stack_boundary function in 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 invalid variable stack read operations.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 01/19/2023
The vulnerability identified as CVE-2017-17857 resides within the Linux kernel's BPF (Berkeley Packet Filter) verifier component, specifically in the check_stack_boundary function located in kernel/bpf/verifier.c. 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 or potentially achieve more severe consequences. The vulnerability stems from improper handling of invalid variable stack read operations during the BPF program verification process, which is designed to ensure that BPF programs execute safely without compromising system integrity.
The technical implementation of this vulnerability occurs when the BPF verifier encounters malformed or invalid stack operations during program validation. The check_stack_boundary function fails to properly validate stack access boundaries, allowing malicious BPF programs to manipulate stack pointers in ways that bypass normal safety checks. This mismanagement creates a condition where the verifier can be tricked into accepting programs that would otherwise be rejected, leading to memory corruption when the program executes. The flaw specifically affects the kernel's ability to correctly handle variable-length stack operations, where the verifier does not adequately verify that stack accesses remain within allocated boundaries.
From an operational perspective, this vulnerability presents significant risks to system stability and security. Local attackers can leverage this flaw to cause denial of service conditions by triggering memory corruption that may result in kernel panics or system crashes. The potential for unspecified other impacts suggests that the memory corruption could be exploited to achieve privilege escalation or other malicious outcomes beyond simple system disruption. Since BPF is used extensively for network packet filtering, system monitoring, and various kernel-level operations, exploitation of this vulnerability could compromise the integrity of critical system functions. The attack vector requires local access to the system, making it particularly concerning for environments where untrusted users might have shell access or where privilege escalation opportunities exist.
Mitigation strategies for CVE-2017-17857 should focus on immediate kernel updates to versions that contain the patched verifier implementation. System administrators should prioritize applying security patches from their respective distribution vendors as soon as available. Additional protective measures include implementing strict BPF program validation policies, monitoring for unusual stack operations, and considering the restriction of BPF program loading capabilities where possible. The vulnerability aligns with CWE-129, which addresses improper validation of array index boundaries, and represents a specific instance of improper input validation that can lead to memory corruption. From an ATT&CK framework perspective, this vulnerability could be categorized under privilege escalation techniques, specifically targeting kernel-level vulnerabilities to gain elevated system privileges. Organizations should also implement monitoring solutions that can detect anomalous stack behavior patterns and consider network segmentation to limit potential attack surfaces where BPF functionality is utilized. The patch for this vulnerability specifically addresses the stack boundary checking logic to ensure proper validation of variable stack read operations before allowing program execution.