Medium [CVE-2026-64508] Support for hardening against JIT spraying
This medium-severity Red Hat Linux advisory covers CVE-2026-64508 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8.
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Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: Support for hardening against JIT spraying The BPF JIT allocator packs many small programs into larger executable allocations and reuses space within those allocations as programs are loaded and freed.
When fresh code is written into space that a previous program occupied, an indirect jump into the new program can reuse a branch prediction left behind by the old one. Flush the indirect branch predictors before reusing JIT memory so that indirect jumps into a newly written program don't reuse predictions from an old program that occupied the same space.
Introduce bpf_arch_pred_flush_enabled static key and bpf_arch_pred_flush static call for flushing the branch predictors on JIT memory reuse. Architectures that need a flush, can update it to a predictor flush function.
By default, its a NOP and does not emit any CALL. Allocations larger than a pack are not covered by this flush.
That is safe because cBPF programs (the unprivileged attack surface) are bounded well below a pack size. Issue a warning if this assumption is ever violated while the flush is active.
A flaw was found in the Linux kernel's Berkeley Packet Filter (BPF) Just-In-Time (JIT) compiler. This could allow an attacker to bypass security hardening mechanisms, potentially leading to information disclosure or other impacts.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative. Check it before change work.
Official advisory · high-confidence parse· fetched 1 month ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists. Confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 1 month ago·verify at source
Mitigation checklist
- To mitigate this issue on systems where unprivileged BPF is enabled, configure the kernel to disallow unprivileged users from loading BPF programs. 1. Temporarily apply the configuration at runtime: # sysctl -w kernel.unprivileged_bpf_disabled=1 2. To make this setting persistent across system reboots, write the parameter to a sysctl configuration file: # echo "kernel.unprivileged_bpf_disabled = 1" > /etc/sysctl.d/99-disable-unprivileged-bpf.conf # sysctl --system Caveats: Disabling unprivileged BPF prevents unprivileged user processes and unprivileged containers from loading BPF programs, which may impact non-root monitoring or tracing tools. Privileged accounts and processes retaining CAP_SYS_ADMIN or CAP_BPF are unaffected and can still load programs. Modifying this sysctl setting takes effect immediately and does not require a system restart or service reload.
Official advisory · high-confidence parse· fetched 1 month ago·verify at source
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