CVE-2026-74506

Received Received - Intake

Use-After-Free in Linux Kernel AFS Module

Publication date: 2026-08-15

Last updated on: 2026-08-17

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: afs: Fix UAF when sending a message In afs_make_call(), there's a race with async call reception and destruction. If a call is dispatched that doesn't have call->write_iter set (used to specify the data content for FS.StoreData), then the first rxrpc_kernel_send_data() will not set MSG_MORE in the msghdr. Once rxrpc_send_data() queues the last request packet, the response could come in at any time and cause the call to be completed and put. However, afs_make_call() will look at the call again to see it ->write_iter should be handled - something it's only allowed to do if it has its own ref on the call. Whilst this is the case for synchronous calls, it isn't true for async calls such as FS.FetchData. There's also a potential UAF in afs_make_call() in the event that an asynchronous call is being sent, but the call fails in some way (e.g. it gets aborted from the server). The problem there is that afs_make_call() tries to abort a call if the rxrpc send fails, but the asynchronous notification from rxrpc may have caused the afs_call to be torn down. generic/650 plays games with randomly taking CPUs offline, and can interject a significant delay such that the call is deallocated before afs_make_call() gets to check call->write_iter - and a UAF ensues (caught by KASAN). BUG: KASAN: slab-use-after-free in afs_make_call+0x1c90/0x2210 [kafs] Read of size 8 at addr ffff888035e050e8 by task fsstress/1409 Fix this by making afs_make_op_call() give the op->call its own ref rather than transferring the caller's ref to it and then dropping the ref when afs_make_call() returns. This also means that the afs_make_call() func never loses its ref on the call now.

CVSS Scores

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Meta Information

Published

2026-08-15

Last Modified

2026-08-17

Generated

2026-09-04

AI Q&A

2026-08-15

EPSS Evaluated

2026-09-03

NVD

CVE-2026-74506

EUVD

EUVD-2026-59699

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This is a Use-After-Free (UAF) vulnerability in the Linux kernel's AFS (Andrew File System) implementation. It occurs due to a race condition between asynchronous call reception and destruction in afs_make_call(). When a call is dispatched without call->write_iter set, the system fails to properly handle the call's lifecycle, leading to potential memory corruption if the call is completed or torn down prematurely.

Detection Guidance

This vulnerability is specific to the Linux kernel's AFS (Andrew File System) implementation and may not have direct network detection methods. Focus on kernel logs for KASAN or slab-use-after-free errors related to afs_make_call. Check for crashes or kernel panics with messages like 'slab-use-after-free in afs_make_call'.

Impact Analysis

This vulnerability could allow an attacker to cause a system crash or execute arbitrary code with kernel privileges. It may lead to denial-of-service conditions or unauthorized access to sensitive data, depending on the attacker's capabilities and system configuration.

Compliance Impact

This vulnerability is a use-after-free (UAF) issue in the Linux kernel's AFS (Andrew File System) implementation. It does not directly relate to data privacy, access controls, or audit logging required by standards like GDPR or HIPAA. The impact is primarily on system stability and integrity rather than compliance with these regulations.

Mitigation Strategies

Update the Linux kernel to the latest stable version that includes the fix for this vulnerability. If immediate patching is not possible, consider disabling the AFS module (afs) if it is not required on your system.

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