CVE-2026-89761

Status: UPDATED  |  Advisory ID: CVE-2026-89761

Key Details

Affected Products, Subsystems & Sectors

What to Know

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

apparmor: fix out-of-bounds write when null terminating a label vec

aa_vec_unique() null terminates at vec[n - dups] when VEC_FLAG_TERMINATE

is passed. If the components are all distinct no duplicates are dropped,

dups is 0 and the terminator goes to vec[n], so the caller has to provide

room for n + 1 entries.

aa_label_strn_parse() sets up its vector with vec_setup(profile, vec, len,

gfp) and then calls aa_vec_unique(vec, len, VEC_FLAG_TERMINATE), but

vec_setup() does not reserve the terminator entry. Up to LOCAL_VEC_ENTRIES

it uses the local array of LOCAL_VEC_ENTRIES pointers, above that it

allocates exactly len pointers. The terminator therefore lands one entry

past the end of the local array when len is LOCAL_VEC_ENTRIES, and one

entry past the end of the allocation when len is larger.

len comes from the number of "//&" separated components in the label name

and label_count_strn_entries() does not bound it. An unprivileged task

reaches the parse by writing to /proc/self/attr/apparmor/current or through

lsm_set_self_attr(2), both of which go through do_setattr(), and the name

is parsed before the change_profile permission is checked.

The query_label() path behind the securityfs .access file, which is

mode 0666, performs no permission check at all. Every component has to

resolve to a loaded profile, so a system with policy loaded is required.

The other two VEC_FLAG_TERMINATE users work on a label vec that

aa_label_alloc() has already sized with "+ 1 for null terminator entry on

vec". Reserve the same entry in vec_setup() and DEFINE_VEC(). Passing

len + 1 from the caller instead would move len == LOCAL_VEC_ENTRIES out of

the local array and into kzalloc(). (NVD)

What to Do

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

References