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.
Published: 2026-09-17
Score: 7.1 High
EPSS: < 1% Very Low
KEV: No
Impact: Out-of-bounds read that may allow privilege escalation
Action: Patch Immediately
AI Analysis

Impact

An integer overflow in AppArmor’s verify_tags function allows an attacker to supply a crafted policy that causes the function to read past the bounds of the tagset table. The overflow bypasses the bounds check, leading to an out-of-bounds read during policy load. This read can expose kernel memory contents and potentially enable privilege escalation or confidential data disclosure.

Affected Systems

Linux kernel; affected products are Linux:Linux, but the specific kernel releases impacted are not listed in the CVE data. Administering the fix requires applying the kernel patch that addresses the overflow in verify_tags.

Risk and Exploitability

The vulnerability has a CVSS score of 7.1 and an EPSS score of less than 1%, indicating low to moderate exploitation probability. It is not listed in the CISA KEV catalog. The flaw can be exploited by an unprivileged process inside a nested user namespace with the sysctl unprivileged_userns_apparmor_policy set to 1, which allows loading of custom AppArmor profiles. The attack path involves supplying a malicious policy blob that triggers the overflow during verify_tags, leading to the out-of-bounds read.

Generated by OpenCVE AI on September 19, 2026 at 15:10 UTC.

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

  • Apply the kernel patch that fixes the integer overflow in verify_tags().
  • Upgrade the system to a Linux kernel version that includes the CVE-2026-90246 fix.
  • Disable policy loading for unprivileged user namespaces by setting sysctl unprivileged_userns_apparmor_policy=0 or removing the CAP_MAC_ADMIN capability from processes that need not load AppArmor policies.

Generated by OpenCVE AI on September 19, 2026 at 15:10 UTC.

Tracking

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Advisories

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History

Sat, 19 Sep 2026 04:00:00 +0000

Type Values Removed Values Added
Weaknesses CWE-125
CWE-190

Fri, 18 Sep 2026 21:30:00 +0000

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 7.1, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H'}

Thu, 17 Sep 2026 16:30:00 +0000

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

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-09-18T17:54:09.848Z

Reserved: 2026-09-11T19:38:34.795Z

Link: CVE-2026-90246

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-09-17T17:17:20.677

Modified: 2026-09-18T18:17:50.873

Link: CVE-2026-90246

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-19T15:15:14Z

Weaknesses