CVE-2026-93245 in Linux
Summary
by MITRE • 09/24/2026
In the Linux kernel, the following vulnerability has been resolved:
apparmor: policy_int make sure list heads are initialized before fail path
If profile create fails before policy_init is complete the list heads are not properly initialized causing profile_free() sanity checks to trigger the following splat.
AppArmor WARN aa_policy_destroy: (((!list_empty(&policy->profiles) && (&policy->profiles)->prev != ((void *) 0x122 + (0xdead000000000000UL))))): WARNING: security/apparmor/lib.c:509 at aa_policy_destroy+0x164/0x1b0 security/apparmor/lib.c:509, CPU#0: syz.0.17/5541 Modules linked in: CPU: 0 UID: 0 PID: 5541 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:aa_policy_destroy+0x16b/0x1b0 security/apparmor/lib.c:509 Code: 85 ed 7e 4d e8 96 bc 37 fd 5b 41 5c 41 5e 41 5f 5d e9 19 27 4e 07 cc e8 83 bc 37 fd 48 8d 3d 0c f0 d3 0b 48 c7 c6 a4 eb 38 8e <67> 48 0f b9 3a e9 04 ff ff ff e8 66 bc 37 fd 48 8d 3d ff ef d3 0b RSP: 0018:ffffc9000345eaa0 EFLAGS: 00010293 RAX: ffffffff848f530d RBX: ffff88803f734800 RCX: ffff88801af2a580 RDX: 0000000000000000 RSI: ffffffff8e38eba4 RDI: ffffffff90634320 RBP: 0000000000000000 R08: 0000000000000cc0 R09: 00000000ffffffff R10: dffffc0000000000 R11: fffffbfff1d95913 R12: dead000000000122 R13: ffff88803f734800 R14: ffff88803f734828 R15: dffffc0000000000 FS: 00007f5f6a1836c0(0000) GS:ffff88808c519000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055d02407b048 CR3: 0000000012aa9000 CR4: 0000000000352ef0 Call Trace: <TASK> aa_free_profile+0x9d/0x9f0 security/apparmor/policy.c:334 aa_alloc_profile+0x1e4/0x3e0 security/apparmor/policy.c:416 unpack_profile security/apparmor/policy_unpack.c:1153 [inline]
aa_unpack+0x17db/0x7430 security/apparmor/policy_unpack.c:1748 aa_replace_profiles+0x226/0x2a20 security/apparmor/policy.c:1183 policy_update+0x234/0x4a0 security/apparmor/apparmorfs.c:505 profile_load+0x1cb/0x320 security/apparmor/apparmorfs.c:522 vfs_write+0x296/0xba0 fs/read_write.c:685 ksys_write+0x150/0x270 fs/read_write.c:739 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f5f6939e0d9 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f5f6a183028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007f5f69625fa0 RCX: 00007f5f6939e0d9 RDX: 0000000000000041 RSI: 0000200000000400 RDI: 0000000000000003 RBP: 00007f5f6a183090 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 R13: 00007f5f69626038 R14: 00007f5f69625fa0 R15: 00007ffe23725c18
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Analysis
by VulDB Data Team • 09/25/2026
The Linux kernel's AppArmor security module contains a logic flaw in the policy initialization sequence that can lead to memory corruption and system instability. Specifically, when creating an application profile via the apparmorfs interface, if the operation fails before the full policy structure is initialized, the list heads within the policy object are not properly set up. This oversight occurs because the error handling path does not account for partially constructed objects where initialization routines were interrupted or failed partway through execution. Consequently, when the kernel attempts to clean up this incomplete profile by calling aa_free_profile and subsequently aa_policy_destroy, it encounters a data structure with invalid list pointers rather than properly initialized empty lists.
This improper state triggers a sanity check within the aa_policy_destroy function located in security/apparmor/lib.c. The code verifies that if profiles exist in the policy's linked list, their previous pointer must not point to a specific corrupted magic value used for debugging and detection of use-after-free or double-free conditions. In this scenario, because the list heads were never initialized during the failed creation attempt, they retain garbage values or uninitialized memory states. The check fails, causing the kernel to emit a warning splat indicating that the prev pointer is pointing to an invalid address pattern (specifically 0xdead000000000122). This results in a Denial of Service condition where the system logs critical warnings and potentially panics or becomes unstable depending on configuration, effectively disrupting the security enforcement capabilities of the host.
From a technical classification perspective, this vulnerability aligns with CWE-665, Improper Initialization, as it involves failing to properly initialize data structures before they are used in subsequent operations such as deallocation. It also relates to CWE-209, Generation of Error Condition Without Taking Action, or more accurately CWE-754, Improper Check for Unusual or Exceptional Conditions, because the error path does not ensure structural integrity before proceeding to cleanup routines. In terms of attack vectors and detection, this issue is relevant to MITRE ATT&CK technique T1068, Exploitation for Privilege Escalation, although in its current manifestation it primarily serves as a local denial-of-service vector rather than an immediate privilege escalation path. An attacker would need the ability to write malformed or triggering data to the apparmorfs interface, which typically requires specific permissions depending on the AppArmor profile configuration of the calling process.
The operational impact is limited to systems where users have write access to the AppArmor policy update interfaces and can trigger rapid creation failures during initialization. While this does not directly allow an unprivileged user to bypass security controls or execute arbitrary code, it degrades system reliability by causing kernel warnings and potential crashes. For administrators running critical infrastructure, such instability is unacceptable as it undermines the availability of the host operating system. The vulnerability highlights a common class of bugs in kernel subsystems where error paths are not meticulously aligned with initialization sequences, leading to inconsistent object states during teardown operations.
Mitigation for this issue involves applying the upstream Linux kernel patch that ensures list heads are initialized before any failure path is taken during profile creation. System administrators should ensure their kernels are updated to versions containing this fix. Additionally, defense-in-depth strategies such as restricting write access to apparmorfs to only trusted administrative users can reduce the attack surface. Monitoring system logs for AppArmor-related warnings and splats can also help in identifying systems that may be susceptible or have already experienced issues related to policy management errors. Regular auditing of kernel updates and adherence to vendor security advisories are essential practices to maintain the integrity and availability of Linux-based environments relying on mandatory access control mechanisms like AppArmor.