CVE-2026-92516 in Linux
Summary
by MITRE • 09/17/2026
In the Linux kernel, the following vulnerability has been resolved:
bpf: Fix offset warn check for bpf_res_spin_lock
Sashiko pointed out correctly that the case statement for BPF_RES_SPIN_LOCK incorrectly checks offset for BPF_SPIN_LOCK. Fix it by checking res_spin_lock_off instead.
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Analysis
by VulDB Data Team • 09/18/2026
The Linux kernel's eBPF subsystem provides a powerful mechanism for running sandboxed programs in the kernel, enabling high-performance networking, observability, and security monitoring capabilities. A critical aspect of ensuring the safety and stability of these programs is the verifier, which analyzes bytecode before execution to prevent invalid memory accesses, infinite loops, or other unsafe operations. Within this verification process, specific instructions are designated for managing synchronization primitives such as spin locks, which are essential for preventing race conditions in concurrent kernel environments. The BPF_RES_SPIN_LOCK instruction type represents a resolved reference to a spin lock object that has been previously allocated and verified by the verifier.
A recent analysis identified an inconsistency within the offset validation logic associated with this specific instruction type. Specifically, when processing cases involving BPF_RES_SPIN_LOCK, the kernel code incorrectly performed its bounds checking against the generic BPF_SPIN_LOCK structure rather than the dedicated res_spin_lock_off field intended for resolved references. This misalignment in data structure access means that the verifier was not accurately validating whether the offset used to access the spin lock metadata remained within valid boundaries defined by the current program context and allocated resources. Such a discrepancy represents a fundamental flaw in the static analysis logic, where the validation mechanism fails to enforce strict memory safety constraints for this particular class of operations.
The operational impact of this vulnerability is significant because it undermines the integrity guarantees provided by the eBPF verifier. If an attacker or a buggy program can exploit this incorrect offset check, they may be able to bypass bounds verification checks designed to prevent out-of-bounds reads or writes into kernel memory structures associated with spin locks. This could potentially lead to unauthorized access to sensitive kernel data, corruption of synchronization primitives leading to system instability or denial of service through kernel panics, or in more severe scenarios, the escalation of privileges if the corrupted state allows for further exploitation vectors. The flaw highlights how subtle errors in type-specific validation logic can compromise the entire security model of a sandboxed execution environment like eBPF.
From an industry standards perspective, this vulnerability aligns with CWE-20 Improper Input Validation and CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer. The failure to correctly validate the offset against the appropriate data structure field constitutes a classic input validation error where the system processes external or internal inputs without ensuring they conform to expected constraints relative to their specific context. Furthermore, in terms of attack taxonomy such as MITRE ATT&CK for Enterprise and ICS, this type of vulnerability facilitates techniques related to Defense Evasion by allowing malicious eBPF programs to bypass security controls implemented via kernel hooks, potentially enabling persistence or credential access without detection by standard monitoring tools that rely on the assumption that verifier-enforced boundaries are strictly maintained.
To mitigate this risk, it is imperative for system administrators and developers utilizing Linux kernels with affected versions to apply the provided patch immediately. The fix involves correcting the case statement logic to reference res_spin_lock_off instead of BPF_SPIN_LOCK during offset validation. This ensures that the bounds checking accurately reflects the memory layout and constraints applicable to resolved spin lock references. Organizations should verify their kernel version status against vendor advisories and prioritize updates for systems running eBPF-based security or networking solutions, as these are most likely to be exposed to untrusted program inputs where such a verification bypass could be leveraged. Regular auditing of eBPF programs loaded into production environments remains essential to ensure compliance with expected behavioral constraints even after patching.