CVE-2026-47332: Ubuntu Linux AppArmor Out-of-Bounds Read Information Disclosure

Technical summary

CVE-2026-47332 is an out-of-bounds read vulnerability in the AppArmor SAUCE patches present in Ubuntu Linux 6.8, 6.17, and 7.0. The root cause is improper size validation of an internal structure used in notification handling code. This validation failure permits an unprivileged local user to trigger an out-of-bounds memory read, allowing extraction of data from adjacent slab objects in the kernel heap. The vulnerability is classified as CWE-125 (Out-of-bounds Read) and requires no user interaction or elevated privileges to trigger.

Business impact

This vulnerability creates a local information disclosure channel that can compromise system confidentiality. Organizations running affected Ubuntu versions face risk of sensitive kernel data being read by any local user account. In multi-tenant environments, containerized deployments, or shared hosting scenarios, this could allow one tenant or user to spy on kernel memory structures belonging to other users or system components. The leaked information could facilitate privilege escalation attacks or reveal cryptographic material, indirectly enabling further compromise of system or application security.

Affected systems

The vulnerability affects Ubuntu Linux kernel versions 6.8, 6.17, and 7.0 specifically. These are relatively recent kernel releases; verify your systems' kernel version using 'uname -r'. The issue is confined to Ubuntu distributions and relates specifically to the AppArmor SAUCE (Secure And UbuntuCustom Extensions) patch set. Verify your distribution (ubuntu vs. derived distributions) and kernel version against the affected range before concluding impact.

Exploitability

This vulnerability has a low barrier to exploitation. It requires only local user access—no special privileges, no user interaction, and minimal complexity to trigger. An unprivileged attacker can reliably craft input to the AppArmor notification handling mechanism to cause the out-of-bounds read. The deterministic nature and low privilege requirement make this a practical risk in any environment where untrusted local users have shell access or where privilege boundaries are weak (e.g., poorly isolated containers).

Remediation

Canonical has released patched kernel versions addressing this AppArmor validation flaw. Organizations must update their Ubuntu systems to the next available kernel version in the 6.8, 6.17, or 7.0 series that includes the fix, or transition to a later stable kernel line if available. Apply updates through standard Ubuntu package management (apt update && apt upgrade or unattended-upgrades). Kernel updates typically require a reboot to take effect. Verify successful patching by confirming the updated kernel version at next boot.

Patch guidance

1. Check current kernel version: run 'uname -r' and confirm if it matches 6.8, 6.17, or 7.0 exactly. 2. Enable Canonical's security advisories and subscribe to ubuntu-security-announce mailing list for notification of available patches. 3. Schedule a maintenance window and apply kernel updates via your standard patch management process (apt-get, Landscape, or unattended-upgrades). 4. Test kernel updates in non-production environments first, particularly in virtualized or containerized infrastructure. 5. Reboot affected systems after kernel installation to load the patched version. 6. Post-reboot, verify the kernel version no longer falls within the vulnerable range. 7. For systems where reboots are constrained, evaluate live patching alternatives if available through your Ubuntu support contract.

Detection guidance

Detection of exploitation attempts is challenging because the vulnerability is triggered through normal AppArmor notification handling. Monitor for: unusual processes attempting to read kernel memory or slab contents; repeated failed or suspicious AppArmor denial events in audit logs (check /var/log/audit/audit.log); and processes spawned by non-root users engaging in atypical memory introspection. Kernel Address Space Layout Randomization (KASLR) and other mitigations reduce but do not eliminate the practical usefulness of the leak. Consider behavioral monitoring for processes attempting memory scanning or information gathering. Implement AppArmor or SELinux policies to restrict unprivileged users' access to /proc and /sys interfaces that could be combined with this flaw for more effective exploitation.

Why prioritize this

Although the CVSS score is moderate (5.5/MEDIUM), the practical risk warrants prioritization for timely patching. The vulnerability requires only local access, is trivial to trigger, and directly enables information disclosure—a foundational step in multi-stage attacks. In environments with shared user accounts, cloud tenants, or container sprawl, an unprivileged attacker gaining kernel memory read access is a serious concern. The issue affects recent, commonly-deployed Ubuntu kernel versions, making it broadly relevant. Organizations should treat this as high-priority for systems in shared environments and medium-priority for dedicated servers with restricted local access.

Risk score, explained

The CVSS:3.1 score of 5.5 (MEDIUM) reflects an attack vector requiring local access and low privileges, with a high confidentiality impact but no integrity or availability impact. The scoring is accurate but conservative: the deterministic exploitability, lack of complexity, and information disclosure impact in multi-tenant settings justify moving such issues toward the higher end of remediation priority within your risk framework, particularly if your threat model includes insider threats or compromised low-privilege accounts.

Frequently asked questions