CVE-2026-99226
Received Received - Intake

Use-After-Free in Linux Kernel Keyring Lookup

Publication date: 2026-11-02

Last updated on: 2026-11-02

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: keys: Avoid the owner account dereference in named keyring lookup Named keyring lookup must keep the storage containing the owner UID alive through the namespace mapping check. find_keyring_by_name() reads keyring->user->uid under keyring_name_lock, but that lock protects the keyring's name entry and allocation, not its separate key_user. A named session-keyring join can overlap a privileged KEYCTL_CHOWN on another CPU. If the keyring holds the last reference to its old dynamic key_user and the ownership transfer succeeds, the following ordering is possible: Named join Chown find_keyring_by_name() keyctl_chown_key() read_lock(keyring_name_lock) down_write(key->sem) load old keyring->user replace key->user and key->uid up_write(key->sem) key_put(key) key_user_put(old user): free read old user->uid read_unlock(keyring_name_lock) Chown neither takes keyring_name_lock nor key_session_mutex, so it can free the old account between the pointer load and the UID read. The lookup then reads freed memory even though the keyring itself is alive. Use keyring->uid for the mapping check. key_alloc() initializes this inline owner UID and keyctl_chown_key() updates it on chown. The existing name lock keeps its containing keyring allocated throughout the check, so lookup no longer depends on the account's lifetime. This also matches the owner UID used by the permission check. KASAN report as below: BUG: KASAN: slab-use-after-free in find_keyring_by_name+0x577/0x5d0 Read of size 4 at addr ffff8881128ae2ec by task keycase/500

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Meta Information

Published
2026-11-02
Last Modified
2026-11-02
Generated
2026-11-02
AI Q&A
2026-11-02
EPSS Evaluated
N/A
NVD
CVE-2026-99226

Affected Vendors & Products

Showing 9 associated CPEs
Vendor Product Version / Range
Linux Linux 2ea190d0a006ce5218baa6e798512652446a605a
Linux Linux 2ea190d0a006ce5218baa6e798512652446a605a
Linux Linux 2ea190d0a006ce5218baa6e798512652446a605a
Linux Linux 2ea190d0a006ce5218baa6e798512652446a605a
Linux Linux 2ea190d0a006ce5218baa6e798512652446a605a
Linux Linux 2ea190d0a006ce5218baa6e798512652446a605a
Linux Linux 2ea190d0a006ce5218baa6e798512652446a605a
Linux Linux 2ea190d0a006ce5218baa6e798512652446a605a
Linux Linux 2.6.30

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves a use-after-free issue in named keyring lookup. The problem occurs when a named session-keyring join overlaps with a privileged KEYCTL_CHOWN operation on another CPU. The lookup function reads freed memory because the keyring's owner account is dereferenced without proper synchronization, leading to a slab-use-after-free error.

Detection Guidance

This vulnerability is specific to the Linux kernel and requires kernel-level detection. Check if your kernel version is affected by running: uname -a. If your kernel version matches affected versions, monitor for slab-use-after-free errors in kernel logs using: dmesg | grep -i "slab-use-after-free". No direct user-space commands detect this issue.

Impact Analysis

This vulnerability could allow an attacker to execute arbitrary code or cause a denial of service by exploiting the use-after-free condition. It may lead to system crashes, privilege escalation, or unauthorized access if successfully exploited.

Compliance Impact

This vulnerability involves a use-after-free flaw in the Linux kernel's keyring subsystem, which could lead to memory corruption and potential privilege escalation. While not directly impacting GDPR or HIPAA compliance, such vulnerabilities may compromise system integrity, potentially leading to unauthorized access to sensitive data. This could violate principles of data protection and confidentiality required by these regulations.

Mitigation Strategies

Apply the latest kernel security patches immediately. Update your Linux distribution to a version containing the fix. If patching is not immediately possible, restrict access to keyctl operations via kernel module restrictions or SELinux policies until patched.

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