CVE-2026-90246

Status: UPDATED  |  Advisory ID: CVE-2026-90246

Key Details

Affected Products, Subsystems & Sectors

What to Know

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

apparmor: fix integer overflow in verify_tags() bounds check

verify_tags() validates the tagset table unpacked from a policy blob.

For each set it reads a count and checks that advancing the index by

that count stays inside sets.table[]:

u32 cnt = tags->sets.table[i];

if (i+cnt >= tags->sets.size) {

i, cnt and sets.size are all u32, so i+cnt is evaluated modulo 2^32.

sets.table[] is filled by unpack_tagsets() with aa_unpack_u32(), so

every entry is a raw unbounded 32-bit word taken from the policy blob,

and verify_tags() is the function that is supposed to validate it. A

count close to U32_MAX makes the sum wrap to a small value, the guard

passes, and the inner loop then walks sets.table[++i] past the end of

the kcalloc(size, sizeof(u32)) allocation.

Note that sets.size is bounded by 65535, because unpack_tagsets() reads

it with aa_unpack_array() as a u16, so the wrap cannot be reached by

growing the table; it is reached purely through the attacker-supplied

count.

With sets.size = 2 and sets.table = { 0, 0xffffffff }:

i = 0: cnt = 0, guard 0 + 0 >= 2 is false, inner loop does not run

i = 1: cnt = 0xffffffff, guard (1 + 0xffffffff) mod 2^32 == 0 >= 2 is

false, so the guard is bypassed and the inner loop reads

sets.table[2] -- one element past a two element allocation

The walk continues until an out-of-bounds value happens to be >=

hdrs.size or the access faults, so a crafted policy yields an

out-of-bounds read on the policy load path

(aa_replace_profiles -> aa_unpack -> unpack_policydb -> unpack_tags ->

verify_tags). unpack_tags() runs before the perms and DFA tables are

unpacked, so no other table needs to be well formed to reach it.

Policy load is gated by aa_may_manage_policy(), which checks

CAP_MAC_ADMIN relative to the subject's own user namespace rather than

the init user namespace, so with the default

unprivileged_userns_apparmor_policy=1 the path is reachable from an

unprivileged task in a matched-level nested namespace, not only by a

globally privileged one.

Perform the addition in u64 so that it cannot wrap, restoring the

intended i + cnt < sets.size guarantee. (NVD)

What to Do

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

References