Out-of-bounds Read Affecting kernel-rt-core package, versions *
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Test your applications- Snyk IDSNYK-RHEL10-KERNELRTCORE-20278115
- published30 Sept 2026
- disclosed24 Sept 2026
Introduced: 24 Sep 2026
NewCVE-2026-97420 (opens in a new tab)How to fix?
There is no fixed version for RHEL:10 kernel-rt-core.
NVD Description
Note: Versions mentioned in the description apply only to the upstream kernel-rt-core package and not the kernel-rt-core package as distributed by RHEL.
See How to fix? for RHEL:10 relevant fixed versions and status.
In the Linux kernel, the following vulnerability has been resolved:
bpf: NUL-terminate replaced sysctl value
When writing to sysctls, proc_sys_call_handler() guarantees that the buffer passed to proc handlers is NUL-terminated. If bpf_sysctl_set_new_value() replaces the pending sysctl value, it can hand a replacement buffer directly to proc handlers. However, the helper currently copies only buf_len bytes into that buffer without appending a NUL terminator, leaving downstream parsers vulnerable to out-of-bounds access.
Fix this by appending a '\0' after the replaced value to restore the expected sysctl semantics. Since the helper already rejects buf_len greater than PAGE_SIZE - 1, there is always room for the extra byte.
Reproduced in a QEMU x86_64 guest booted with KASAN while exercising
the sysctl replacement path with a cgroup/sysctl BPF program. The
reproducer targets /proc/sys/net/core/flow_limit_cpu_bitmap, fills
the original user write buffer with non-zero bytes, and overrides the
sysctl value so the replacement buffer lacks a terminating NUL. Under
that setup, the pre-fix kernel reported:
BUG: KASAN: slab-out-of-bounds in strnchrnul+0x72/0x90 Read of size 1 at addr ffff88800de57000 by task repro_patch3/66 CPU: 0 UID: 0 PID: 66 Comm: repro_patch3 Not tainted 7.1.0-rc3-00269-g8370ca1f87cc #6 PREEMPT(lazy) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x68/0xa0 print_report+0xcb/0x5e0 ? __virt_addr_valid+0x21d/0x3f0 ? strnchrnul+0x72/0x90 ? strnchrnul+0x72/0x90 kasan_report+0xca/0x100 ? strnchrnul+0x72/0x90 strnchrnul+0x72/0x90 bitmap_parse+0x37/0x2e0 flow_limit_cpu_sysctl+0xc6/0x840 ? __pfx_flow_limit_cpu_sysctl+0x10/0x10 ? __kvmalloc_node_noprof+0x5ba/0x870 proc_sys_call_handler+0x31d/0x480 ? __pfx_proc_sys_call_handler+0x10/0x10 ? selinux_file_permission+0x39f/0x500 ? lock_is_held_type+0x9e/0x120 vfs_write+0x98e/0x1000 ... </TASK> The buggy address is located 0 bytes to the right of allocated 4096-byte region [ffff88800de56000, ffff88800de57000) With this fix applied, rerunning the same sysctl-targeted path yields no corresponding KASAN reports.
References
- https://bugzilla.redhat.com/show_bug.cgi?id=2540519
- https://access.redhat.com/security/cve/CVE-2026-97420
- https://git.kernel.org/stable/c/3b2814dd842a565fcf9cc370156e1ba9eae16239
- https://git.kernel.org/stable/c/76c14b10f50eb0afcc76e244562fa2d8c661e224
- https://git.kernel.org/stable/c/a66e3b5bacf38d6ab29fa05a9754f7a114485605