CVE-2026-97944

Status: UPDATED  |  Advisory ID: CVE-2026-97944

Key Details

Affected Products, Subsystems & Sectors

What to Know

In the Linux kernel, the following vulnerability has been resolved:

x86/cfi: Fix FineIBT hash offset in cfi_get_func_hash()

The switch of the FineIBT preamble from "subl $hash, %r10d" to the

shorter "subl $hash, %eax" moved the hash immediate from offset 7 to

offset 5 of the preamble. fineibt_preamble_hash was updated to match,

but the open-coded offset in cfi_get_func_hash() was missed and it

still reads the hash at offset 7.

cfi_get_func_hash() is used by the BPF JIT to give a struct_ops

trampoline the CFI hash of the stub function it stands in for. With

FineIBT the trampoline now gets the upper half of the real hash

followed by the first two bytes of the next instruction, so the first

indirect call from the kernel into a struct_ops program,

tcp_init_congestion_control() calling ->init() of a BPF congestion

control for example, fails the FineIBT check and the kernel dies with

a CFI failure.

Move the FineIBT preamble template and its offset defines above

cfi_get_func_hash() and use fineibt_preamble_hash there, so every

reader of the preamble shares one definition of its layout. The

CFI_FINEIBT arm is only built with CONFIG_FINEIBT, the only

configuration in which cfi_mode can take that value.

cfi_get_func_arity() does not need the same treatment: the __bhi_args

call whose displacement it reads still ends at the function address. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References