CVE-2026-64507 in Linux
Summary
by MITRE • 07/25/2026
In the Linux kernel, the following vulnerability has been resolved:
x86/bugs: Enable IBPB flush on BPF JIT allocation
Enable hardening against JIT spraying when Spectre-v2 mitigations are in use. Specifically, issue an IBPB flush on BPF JIT memory reuse. Skip enabling the IBPB flush if the BPF dispatcher is already using a retpoline sequence.
This hardening applies only when BPF-JIT is in use. Guard the enabling under CONFIG_BPF_JIT so that bugs.c still builds with CONFIG_BPF_JIT=n.
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Analysis
by VulDB Data Team • 07/25/2026
The vulnerability addressed in this linux kernel update relates to speculative execution side-channel attacks targeting the branch predictor and instruction buffer mechanisms. This issue specifically affects systems implementing spectre-v2 mitigations where the kernel's bpf just-in-time compiler creates executable memory regions that could potentially be exploited through jit spraying techniques. The problem arises from insufficient memory management during bpf jit allocation cycles where previously used memory pages might retain speculative execution artifacts that could leak sensitive information across privilege boundaries.
The technical flaw manifests in the x86 architecture's handling of indirect branch prediction buffers during bpf just-in-time compilation processes. When bpf programs are compiled and executed, the kernel allocates executable memory regions that may contain previously used code or data structures. Without proper flushing mechanisms, these memory regions could retain speculative execution state that allows attackers to infer information about other processes or kernel memory through side-channel attacks. The vulnerability specifically impacts systems where spectre-v2 mitigations are enabled but the ibpb (indirect branch prediction barrier) flush mechanism is not properly invoked during bpf jit memory reuse operations.
The operational impact of this vulnerability extends beyond typical bpf execution scenarios to encompass any system running bpf programs with jit compilation enabled. Attackers could potentially exploit this weakness to perform information disclosure attacks by manipulating bpf programs to create predictable memory access patterns that reveal kernel memory contents or process information. The threat is particularly significant in multi-tenant environments or systems where bpf programs are used for network filtering, packet processing, or system monitoring tasks where sensitive data might be processed through the jit compiler. This vulnerability directly relates to common weakness enumeration 1187 which describes insufficient protection against speculative execution side-channel attacks and aligns with attack technique t1059 006 from the att&ck framework which covers command and scripting interpreter for code injection.
The kernel mitigation implemented addresses this issue by enabling ibpb flush operations specifically during bpf jit memory allocation and reuse scenarios. This hardening mechanism ensures that when bpf programs are compiled and executed, any previously used memory pages undergo proper branch prediction buffer flushing to prevent speculative execution artifacts from persisting. The implementation includes conditional logic that skips the ibpb flush when the bpf dispatcher is already using retpoline sequences, preventing unnecessary performance overhead while maintaining security guarantees. The fix is carefully guarded under CONFIG_BPF_JIT configuration option to ensure system compatibility and prevent build failures on systems where bpf jit compilation is disabled.
Security researchers identified this vulnerability through analysis of speculative execution attack vectors in kernel memory management subsystems, particularly focusing on how just-in-time compilers interact with microarchitectural features. The solution represents a targeted approach to mitigating information disclosure risks while maintaining performance characteristics for legitimate bpf operations. This fix demonstrates the ongoing challenge of balancing security hardening with system performance in modern operating systems where complex microarchitectural features introduce new attack surfaces. The mitigation follows established security practices for addressing speculative execution vulnerabilities and aligns with industry recommendations for protecting against side-channel attacks in kernel memory management contexts. The implementation specifically targets the intersection of bpf jit compilation and spectre-v2 mitigations, providing a defense-in-depth approach that addresses both the immediate vulnerability and broader speculative execution attack surface considerations.
The fix represents a critical security enhancement for linux systems running bpf programs with jit compilation enabled, particularly in enterprise environments where bpf is commonly used for network security monitoring, system performance analysis, and containerized application management. The conditional nature of the implementation ensures that systems without bpf jit compilation remain unaffected while providing comprehensive protection for those environments where the vulnerability exists. This update reinforces the importance of maintaining up-to-date kernel versions to protect against evolving speculative execution attack vectors and demonstrates the ongoing need for security researchers and kernel developers to collaborate on addressing complex microarchitectural vulnerabilities in modern computing systems.