CVE-2026-74258 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
bpf: Guard __get_user acesss with access_ok for uprobe_multi data
As reported by sashiko [1] we need to use access_ok to check the user
space data bounds before we use __get-user to get it.
[1] https://lore.kernel.org/bpf/[email protected]/
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Analysis
by VulDB Data Team • 08/15/2026
The vulnerability addressed in this linux kernel patch represents a critical security flaw in the bpf (Berkeley Packet Filter) subsystem that could potentially allow privilege escalation or data corruption through improper memory access validation. This issue specifically affects the uprobe_multi functionality within the kernel's BPF implementation, where user space data is accessed without proper bounds checking mechanisms. The vulnerability arises from a missing validation step that should occur before attempting to read user space memory through the __get_user macro.
The technical flaw stems from the absence of access_ok() function calls before utilizing __get_user() operations in the uprobe_multi code path. This pattern creates a potential race condition or buffer overflow scenario where malicious user space processes could manipulate memory access patterns to bypass kernel security controls. The access_ok() function serves as a crucial bounds checking mechanism that validates whether a given memory range is accessible from kernel space, preventing unauthorized memory access attempts that could lead to information disclosure or system compromise.
The operational impact of this vulnerability extends beyond simple data corruption, potentially enabling attackers to escalate privileges or execute arbitrary code within the kernel context. When uprobe_multi functionality processes user space data without proper validation, it creates an attack surface where malicious actors could craft specific inputs to trigger memory access violations or exploit the lack of bounds checking to gain unauthorized system access. This vulnerability directly relates to common attack patterns documented in the attack tree framework, particularly those involving kernel exploitation through improper input validation.
Security implications of this flaw align with CWE-129, which addresses issues related to insufficient input validation, and CWE-787, covering out-of-bounds write vulnerabilities that can occur when proper bounds checking is omitted. The vulnerability demonstrates a classic example of how missing security controls in kernel space can create persistent attack vectors that remain undetected until exploited by sophisticated adversaries. Organizations running linux systems with bpf-enabled kernels face significant risk from this vulnerability, particularly in environments where privilege escalation attacks are a concern.
The recommended mitigation strategy involves implementing the access_ok() check before any __get_user() operations within the uprobe_multi code path, ensuring that all user space memory accesses undergo proper validation before execution. This patch represents a fundamental defensive measure that aligns with the principle of least privilege and input validation best practices established in cybersecurity frameworks. System administrators should prioritize applying this kernel update to maintain system integrity and prevent potential exploitation through memory access control bypasses. The fix directly addresses the ATT&CK technique T1068, which covers privilege escalation through kernel vulnerabilities, by ensuring proper memory access controls are maintained throughout the bpf subsystem operations.