CVE-2026-90246
apparmor: fix integer overflow in verify_tags() bounds check
Published Sep 17, 2026
CVSS 3.1 · 7.1 High
EPSS < 1%
KEV · Not listed
Description
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.
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.
Affected Products
-
CVE record
-
NVD configurations
No data
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Red Hat packages
No data
-
OpenCVE enrichment
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
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| Linux | Linux | affected |
|
No data.
No data.
| Vendor | Product | Versions | ||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux Kernel |
|
||||||||||||||||||||
| Linux | Linux Kernel |
|
Remediation
Tracking
Advisories
| Source | ID | Title |
|---|---|---|
 Ubuntu USN |
USN-9019-1 | Linux kernel (Azure) vulnerabilities |
| Ubuntu USN |
USN-9020-1 | Linux kernel vulnerabilities |
Metrics
No CVSS v4.0
Attack Vector Local
Attack Complexity Low
Privileges Required Low
Scope Unchanged
Confidentiality Impact High
Integrity Impact None
Availability Impact High
User Interaction None
No CVSS v3.0
No CVSS v2
This CVE is not in the KEV list.
Exploit prediction score: < 1% (0.166% probability within 30 days)
Key SSVC decision points have not yet been added.
References
History
Sep 19, 2026 4:00 AM
Weaknesses updated
View changes
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-125 CWE-190 |
Sep 18, 2026 9:30 PM
Scoring metrics updated
View changes
| Type | Values Removed | Values Added |
|---|---|---|
| Metrics |
cvssV3_1
|
Sep 17, 2026 4:30 PM
Description updated. Title updated. First appearance in the feed. Affected versions updated. Affected vendors updated. Added references
View changes
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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. | |
| Title | apparmor: fix integer overflow in verify_tags() bounds check | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
