CVE-2026-47333: Ubuntu Linux AppArmor Heap Out-of-Bounds Memory Read Vulnerability

Technical summary

CVE-2026-47333 is a heap memory out-of-bounds read vulnerability (CWE-125) affecting AppArmor's notification handling code in Ubuntu Linux kernels 6.8, 6.17, and 7.0. The root cause is incorrect computation of an internal buffer size within the SAUCE (Source and Architecture of Ubuntu Configuration Extensions) patches applied to AppArmor. When an unprivileged local user triggers the affected code path, the DFA (Deterministic Finite Automaton) policy engine receives and processes invalid or out-of-bounds memory contents. This violates memory safety guarantees and can lead to information disclosure.

Business impact

This vulnerability poses a moderate-to-significant operational risk for organizations running affected Ubuntu kernel versions. Unprivileged local users—including regular system accounts, containerized workloads, or SSH users with valid credentials—can extract sensitive kernel memory. Potential impacts include disclosure of cryptographic material, authentication tokens, or other privileged data resident in kernel memory. While not a direct privilege escalation, the information disclosure capability can enable secondary attacks. Systems hosting multi-tenant workloads or untrusted user environments face elevated risk.

Affected systems

Ubuntu Linux systems running kernel versions 6.8, 6.17, or 7.0 are affected. Canonical has released or will release kernel updates addressing this issue. Administrators should verify their running kernel version with 'uname -r' and cross-reference against vendor advisories for affected point releases and available patched versions.

Exploitability

Exploitability is relatively high. The vulnerability requires only local access and unprivileged user privileges (PR:L); no user interaction (UI:N) or special system configuration is needed. Attack complexity is low (AC:L), meaning a basic trigger mechanism is sufficient. However, the vulnerability requires execution of code or interaction with the affected system via local login, SSH, or container escape—it is not remotely exploitable. Canonical has not indicated active exploitation in the wild, and this CVE is not on the CISA Known Exploited Vulnerabilities (KEV) catalog.

Remediation

Patch affected kernel versions immediately. Canonical will release fixed kernel packages for Ubuntu Linux 6.8, 6.17, and 7.0 branches. Enable unattended security updates where policy permits. For systems unable to reboot immediately, evaluate workload isolation and access controls to minimize local user privileges. No workaround exists; kernel patching is the only mitigation.

Patch guidance

Contact your Ubuntu vendor or check the Ubuntu Security Notices (USN) for patched kernel versions addressing CVE-2026-47333. Apply patches to kernel versions 6.8, 6.17, and 7.0 according to your deployment timeline, prioritizing production and multi-tenant systems. Verify patch application and reboot to activate the fixed kernel. Canonical's advisory will specify exact patched version numbers—verify against that source before deployment.

Detection guidance

Monitor system logs for AppArmor denial events or memory access violations that may indicate exploitation attempts. Kernel audit logs ('auditd') can capture suspicious system calls or memory access patterns if AppArmor logging is enabled. In containerized environments, monitor for unexpected memory access errors or crashes in unprivileged user processes. Intrusion detection systems with kernel-level visibility may flag out-of-bounds memory read attempts, though this vulnerability may be difficult to detect retrospectively without specialized profiling.

Why prioritize this

The HIGH CVSS score (7.8) reflects a combination of high confidentiality impact and the low barrier to exploitation (local, unprivileged access). While not remotely exploitable and not yet widely exploited, the information disclosure risk—especially in multi-tenant or containerized environments—warrants rapid patching. Organizations with strict data protection requirements or regulated workloads should prioritize this remediation within their standard critical-patch windows.

Risk score, explained

CVSS 3.1 score 7.8 (HIGH) is derived from the following factors: Attack Vector Local (AV:L) limits remote exploitability; Attack Complexity Low (AC:L) indicates minimal barrier to trigger; Privileges Required Low (PR:L) allows unprivileged users to exploit; User Interaction None (UI:N) means no user action is required; Scope Unchanged (S:U) confines impact to the affected component; Confidentiality High (C:H) reflects potential exposure of kernel memory; Integrity High (I:H) and Availability High (A:H) reflect the ability to cause invalid data processing and system instability. The vector emphasizes the local-only nature while acknowledging the serious information disclosure capability.

Frequently asked questions