Описание
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. The BPF JIT allocator reuses memory space, and when new code is written, an indirect jump into the new program can reuse a branch prediction left behind by an old program. This could allow an attacker to bypass security hardening mechanisms, potentially leading to information disclosure or other impacts. The vulnerability is mitigated by flushing indirect branch predictors before reusing JIT memory.
Отчет
The default Red Hat Enterprise Linux kernel prevents unprivileged users from being able to use eBPF by the kernel.unprivileged_bpf_disabled sysctl. This would require a privileged user with CAP_SYS_ADMIN or root to be able to abuse this flaw reducing its attack space. For the Red Hat Enterprise Linux to confirm the current state, inspect the sysctl with the command: cat /proc/sys/kernel/unprivileged_bpf_disabled The setting of 1 would mean that unprivileged users can not use eBPF, mitigating the flaw.
Меры по смягчению последствий
To mitigate this issue on systems where unprivileged BPF is enabled, configure the kernel to disallow unprivileged users from loading BPF programs.
- Temporarily apply the configuration at runtime:
sysctl -w kernel.unprivileged_bpf_disabled=1
- 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.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 6 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel-rt | Affected | ||
| Red Hat Enterprise Linux 8 | kernel | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel-rt | Affected | ||
| Red Hat Enterprise Linux 9 | kernel-rt | Affected | ||
| Red Hat Enterprise Linux 10 | kernel | Fixed | RHSA-2026:81406 | 12.10.2026 |
| Red Hat Enterprise Linux 9 | kernel | Fixed | RHSA-2026:81552 | 13.10.2026 |
| Red Hat Enterprise Linux 9 | kernel | Fixed | RHSA-2026:81552 | 13.10.2026 |
| Shadow Migration Toolkit for Virtualization for RHEL 10 | kernel | Fixed | RHSA-2026:81406 | 12.10.2026 |
Показывать по
Дополнительная информация
Статус:
6.7 Medium
CVSS3
Связанные уязвимости
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...
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 progra
In the Linux kernel, the following vulnerability has been resolved: b ...
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 pro...
6.7 Medium
CVSS3