CVE-2026-99222

None

CVSS

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EPSS

0.2%

Published

Nov 2, 2026

CISA due date

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Cloudanix analysis

Schedule a fix SSVC: Track

A flaw in how the Linux kernel handles reading certain keys can let an attacker on the same machine crash the system or potentially run code they should not be able to.

Exploitation: Local Privilege
Attacker needs: Low Privilege
Complexity: Moderate
Impact: Data Exposure
Component: OS kernel
Class: Use After Free
Remediation: Upgrade
Effort: Medium
Patch risk: Low

What it actually does

Use-after-free in keyctl_read_key() where the type->read method pointer is dereferenced without holding key->sem, allowing access to freed module memory after type unregistration during module unload.

Why it matters to the business

Linux kernel systems handling cryptographic or network keys face risk of crashes, memory corruption, or potential local privilege escalation, which can disrupt services and require emergency patching across fleets.

How an attack unfolds

An attacker with local access creates or accesses an RxRPC key, triggers concurrent AF_RXRPC module unload and key GC that retypes the key to dead under the semaphore, then performs a read that dereferences the now-freed type method pointer.

How to fix it

Apply the upstream kernel patch that relocates the read method check inside __keyctl_read_key() under the semaphore; rebuild and deploy updated kernel packages to all affected systems.

How to confirm the fix worked

Confirm the fix by inspecting the keyctl_read_key and __keyctl_read_key functions in the patched kernel source to ensure the type check occurs after key_validate under the read semaphore; test with concurrent module unload and key read operations.

Typical attack path

Obtain local execution on target Linux system
Create or reference an AF_RXRPC key
Trigger or race with af_rxrpc module unload and key garbage collection
Invoke keyctl read operation to hit the unprotected type method check
Read from freed module memory leading to crash or controlled execution

How to detect it

Review kernel logs for oops traces referencing keyctl_read_key, unregister_key_type, or af_rxrpc_exit; inspect for concurrent key GC and module unload events around key read operations.

What your security team should do

Prioritize patching Linux kernels within the next maintenance window due to local UAF risk
Monitor for kernel oops or panic logs involving keyctl or af_rxrpc
Restrict unprivileged local keyctl access via LSM or seccomp where feasible
Audit systems for loaded AF_RXRPC module usage before applying updates

The record

In the Linux kernel, the following vulnerability has been resolved: keys: Protect the read method check against type removal keyctl_read_key() checks key->type->read without holding key->sem. A reference keeps the key alive, but does not pin the module containing its type. A surviving RxRPC key can therefore be read while AF_RXRPC is being unloaded: KEYCTL_READ task Module unload and key GC ---------------- ------------------------ lookup_user_key() permission / possession checks load key->type af_rxrpc_exit() unregister_key_type() GC: down_write(key->sem) GC: retype to key_type_dead GC: up_write(key->sem) unregister_key_type() returns free_module() read saved type's read member The final access can read freed module storage. The read invocation in __keyctl_read_key() is already protected by key->sem, but the earlier method check is outside that critical section. Move the method check into __keyctl_read_key(), after key_validate() and under its existing read hold on key->sem. The check and invocation then use the same protected type for length queries and every read retry. The GC cannot retype the key until the semaphore is released, and type unregistration waits for that GC pass before the module can be freed. Return -EOPNOTSUPP when validation succeeds and the type has no read method. A temporary buffer may now be allocated before this result; allocation and copying to userspace remain outside the semaphore.

Affected packages

Ecosystem	Package	Introduced	Fixed