Medium

Linux kernel BPF constant blinding bypass in PROBE_MEM32 stores

IdentifiersCVE-2026-23417CWE-693

CVE-2026-23417 is a flaw in the Linux kernel BPF JIT hardening path. BPF_ST | BPF_PROBE_MEM32 immediate stores were not handled by bpf_jit_blind_insn(), which meant user-controlled 32-bit immediate values could remain unblinded in JIT-compiled native code even when constant blinding was expected to be applied with bpf_jit_harden >= 1. The root cause is an ordering and opcode-handling gap: during verification, convert_ctx_accesses() rewrites certain BPF_ST|BPF_MEM arena pointer stores into BPF_ST|BPF_PROBE_MEM32 before JIT compilation, but the later blinding logic only matched BPF_ST|BPF_MEM and not BPF_ST|BPF_PROBE_MEM32. As a result, the instruction bypassed the intended blinding transformation. The fix adds explicit BPF_ST|BPF_PROBE_MEM32 handling to bpf_jit_blind_insn(), applying the same transformation used for normal immediate stores: loading a blinded immediate into BPF_REG_AX via mov+xor and rewriting the store into a BPF_STX form while preserving PROBE_MEM32 mode so the architecture JIT emits correct arena addressing.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Based on the provided content and scoring, the primary impact is local denial of service. An attacker able to load or influence a vulnerable BPF program can cause user-controlled immediates to survive into JIT-generated native code without the intended hardening transformation, undermining BPF JIT constant blinding. The supplied CVSS vectors indicate no confidentiality or integrity impact and high availability impact, consistent with a crash or similar service disruption in the local kernel attack context.

Mitigation

If you can’t patch tonight, do this now.

If immediate patching is not possible, reduce exposure by restricting untrusted local users' ability to load BPF programs and by disabling or limiting BPF JIT usage/hardening-dependent attack surface where operationally feasible. The vulnerability is only relevant in configurations where BPF JIT compilation is in use and bpf_jit_harden is set to 1 or higher. General least-privilege controls around BPF program loading and kernel attack-surface reduction are appropriate interim measures. Specific temporary mitigations beyond that are not provided in the supplied content.

Remediation

Patch, then assume compromise.

Apply a Linux kernel update containing the fix for CVE-2026-23417, specifically the change that adds BPF_ST|BPF_PROBE_MEM32 handling to bpf_jit_blind_insn() and preserves PROBE_MEM32 mode when rewriting the instruction to BPF_STX. Vendor-provided fixed packages should be used where available. The provided content notes SUSE fixes released on 2026-05-28 for affected product lines including SLES 16.0, SLES for SAP applications 16.0, SUSE Linux Micro 6.2, and openSUSE Leap 16.0, with fixed kernel package version 6.12.0-160000.33.1 referenced for those lines.

PUBLIC EXPLOITS

Exploits

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VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

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VendorProductType

LinuxLinux Kerneloperating_system

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ACTIVITY FEED

Recent activity

2 sources tracked across advisories and community write-ups. News coverage will land here when it surfaces.

2 SOURCESView more in app

No news coverage yet. Advisories and community discussion only.

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Exposure mapping

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Threat actor evidence

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Associated malware

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Detection signatures

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Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

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