Linux Kernel CVE-2025-68208

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

bpf: account for current allocated stack depth in widen_imprecise_scalars()

The usage pattern for widen_imprecise_scalars() looks as follows:

prev_st = find_prev_entry(env, ...); queued_st = push_stack(...); widen_imprecise_scalars(env, prev_st, queued_st);

Where prev_st is an ancestor of the queued_st in the explored states tree. This ancestor is not guaranteed to have same allocated stack depth as queued_st. E.g. in the following case:

def main(): for i in 1..2: foo(i) // same callsite, differnt param

def foo(i): if i == 1: use 128 bytes of stack iterator based loop

Here, for a second 'foo' call prev_st->allocated_stack is 128, while queued_st->allocated_stack is much smaller. widen_imprecise_scalars() needs to take this into account and avoid accessing bpf_verifier_state->frame[*]->stack out of bounds.

The Linux kernel BPF subsystem is affected in versions containing widen_imprecise_scalars() prior to the fix. No specific version range or CPE was provided in the input; affected releases are those before the stable trees represented by the fix commits at git.kernel.org (57e04e2ff56e, 64b12dca2b0a, 9944c7938cd5, b0c8e6d3d866). The four separate stable-branch commits indicate the fix was backported across multiple maintained kernel series. Exact vulnerable version boundaries should be confirmed from each stable branch's changelog, as NVD supplied no CPE match data.