UBUNTU-CVE-2026-99224: High severity ubuntu/linux vulnerability
In the Linux kernel, the following vulnerability has been resolved: keys: Protect the type name while describing a key keyctldescribekey() must keep the key type's name alive until kasprintf() has consumed it. The retained key reference keeps the key and its description alive, but does not pin the module providing its type. The name is passed to kasprintf() without holding key->sem. kvasprintf() uses the saved name pointer in two formatting passes, with a GFPKERNEL allocation between them. With AFRXRPC=m, a task that passes View permission before type retirement can overlap a privileged module unload in this order: 1. KEYCTLDESCRIBE looks up the key, saves key->type->name in the kasprintf() arguments and completes the first formatting pass. 2. While the formatter is delayed before its second pass, afrxrpcexit() calls unregisterkeytype(), which removes the type from the registry and waits for keygckeytype(). 3. The collector takes key->sem for writing, retypes the retained key to keytypedead and completes retirement. Unregistration and module exit return, allowing freemodule() to release the type and name. 4. The formatter resumes its second pass and reads the saved name from released module storage, which can fault in string(). Hold key->sem for reading across kasprintf(). The collector then cannot retype the key or complete retirement until both formatting passes have finished. If retirement wins the lock first, formatting uses the core keytypedead name instead. Release the semaphore immediately after kasprintf(), including on allocation failure, before copying to userspace. Oops report as below: BUG: unable to handle page fault for address: fffffbfff8054794 #PF: supervisor read access in kernel mode #PF: errorcode(0x0000) - not-present page RIP: 0010:string+0x23f/0x470 Call Trace: vsnprintf+0x330/0x1110
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Compensating control
Hold key->sem for reading across kasprintf(), including both formatting passes and any allocation between them; release the semaphore immediately after kasprintf() returns, including on allocation failure, before copying the result to userspace.
Event History
Frequently Asked Questions
Who can realistically trigger this issue?
A local task must be able to invoke KEYCTL_DESCRIBE on a key for which it has View permission. Exploitation also depends on AF_RXRPC being built as a module and overlapping the describe operation with a privileged unload of that module.
What access does an attacker need?
The vector is local and requires low privileges, as reflected by the provided CVSS vector. The task needs View permission on the target key; unloading the affected module is described as a privileged action.
Are systems without the RXRPC module affected by the described race?
The described sequence specifically requires AF_RXRPC=m and the af_rxrpc_exit() path to unregister the key type during module unload. The provided information does not establish the same trigger for systems where that module is unavailable or not unloadable.