CVE-2026-90231
HighCVSS 8.4Exploitation Probability (EPSS)
Low risk5th percentile - higher than 5% of all known CVEs
Summary
A flaw in the Linux kernel AppArmor subsystem affects the unconfined user namespace restriction when a task is already confined by a profile stack. The restriction is not correctly applied, allowing an escape if two transitions through an unconfined profile can be executed. The fix moves the check into the per-profile label build so it is always evaluated against unconfined.
Risk Assessment
A local attacker could bypass AppArmor confinement and gain privileges beyond those intended, undermining application isolation. In environments relying on AppArmor to sandbox services or containers, this may lead to privilege escalation.
Recommendation
Update the Linux kernel to a version containing the fix for CVE-2026-90231. If immediate patching is not possible, consider restricting transitions through unconfined profiles or strengthening AppArmor monitoring.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: apparmor: fix unconfined user namespace restriction forced stack If a task is already confined by a stack the unprivileged transition restriction on unconfined is not correctly, applied. This results in an escape if two transitions through an unconfined profile can be executed. Fix this by pushing the check into the per profile label build. The check will always be done against unconfined and result in a stack of just the unconfined component when necessary.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS

