high CVSS 7.8

CVE-2024-40956·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: dmaengine: idxd: Fix possible Use-After-Free in irq_process_work_list Use list_for_each_entry_safe() to allow iterating through the list and deleting the entry in the iteration process. The descriptor is freed via idxd_desc_complete() and there's a slight chance may cause issue for the list iterator when the descriptor is reused by another thread without it being deleted from the list.

Severity
high
Software
Kernel
Fixed in
6.9.7
Published
2024-07-12

Affected versions

From: 6.7

Until: 6.9.7

Fixed in: 6.9.7

How to fix this CVE

Update your Linux kernel to version 6.9.7 or later to resolve a use-after-free vulnerability in the IDXD DMA engine interrupt handler. This vulnerability could allow local attackers with limited privileges to cause denial of service or potentially execute arbitrary code. Apply the kernel update through your distribution's package manager and reboot your system to activate the patched kernel.

sudo dnf update kernel kernel-devel && sudo reboot

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check your current kernel version with `uname -r` and compare against the affected range (6.7 through 6.9.6)
  2. Step 2: Verify if the IDXD driver is loaded by running `lsmod | grep idxd` or checking for Intel Data Streaming Accelerator devices with `lspci | grep -i accelerator`
  3. Step 3: Search system logs for kernel warnings or crashes related to IDXD using `grep -i 'idxd\|dmaengine' /var/log/kern.log /var/log/messages`
  4. Step 4: After applying the update, confirm the new kernel version is loaded with `uname -r` and verify it shows 6.9.7 or later

FAQ

What is CVE-2024-40956?

CVE-2024-40956 is a use-after-free memory vulnerability in the Linux kernel's IDXD (Intel Data Streaming Accelerator) DMA engine interrupt handler. When processing descriptor completion lists, freed descriptors could be accessed again if they were reused by another thread before being removed from the iteration list, leading to kernel crashes or potential code execution.

Is CVE-2024-40956 being actively exploited?

No, CVE-2024-40956 is not currently listed in CISA's Known Exploited Vulnerabilities (KEV) catalog and no public exploits have been released. However, the vulnerability requires only local access with limited privileges to trigger.

What versions of Kernel are affected by CVE-2024-40956?

Linux kernel versions 6.7 through 6.9.6 are affected. Kernel 6.9.7 and later versions contain the fix.

How do I check if my server is vulnerable to CVE-2024-40956?

Run `uname -r` to check your kernel version. If it reports a version between 6.7 and 6.9.6, you are vulnerable. Additionally, verify IDXD support is present with `grep -i idxd /boot/config-$(uname -r)` or `lsmod | grep idxd`.

Does Defensia detect CVE-2024-40956?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If the Linux kernel is installed on a monitored server, CVE-2024-40956 will appear in your dashboard with remediation steps.

Related Kernel CVEs

CVE-2026-100075CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: RDMA/srpt: Fix srpt_alloc_rw_ctxs() unwind counters When srpt_alloc_rw_ctxs() fails partway through a multi-buffer indirect descriptor, the unwind path destroys RDMA contexts but leaves stale n_rw_ctx and n_rdma values (and a dangling rw_ctxs pointer). Later sq_wr_avail accounting in srpt_queue_response() or srpt_write_pending() can then subtract the wrong number of send queue credits. Reset the counters and clear rw_ctxs after freeing the heap allocation before returning an error.
CVE-2026-64439CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: crypto: krb5 - filter out async aead implementations at alloc krb5_aead_encrypt(), krb5_aead_decrypt() in rfc3961_simplified.c and rfc8009_encrypt(), rfc8009_decrypt() in rfc8009_aes2.c set a NULL completion callback and treat any negative return from crypto_aead_{encrypt,decrypt}() as terminal, falling through to kfree_sensitive(buffer). When the encrypt_name resolves to an async AEAD instance the request returns -EINPROGRESS, the buffer is freed while the backend's worker still holds a pointer, and the worker dereferences the freed slab on completion. KASAN report under UML+SLUB with a synthetic async aead backend bound to krb5->encrypt_name: BUG: KASAN: slab-use-after-free in t5_stub_complete+0x7d/0xc7 The helpers were written synchronously, so filter the async instances out at allocation time instead of plumbing crypto_wait_req() through every call site. Reachable via net/rxrpc/rxgk.c, fs/afs/cm_security.c and net/ceph/crypto.c on systems with an async AEAD provider bound to the krb5 enctype name.
CVE-2026-64066CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: netfs: Fix netfs_read_to_pagecache() to pause on subreq failure Fix netfs_read_to_pagecache() so that it pauses the generation of new subrequests if an already-issued subrequest fails.
CVE-2026-64383CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: smb: client: fix double-free in SMB2_flush() replay SMB2_flush() keeps its response buffer bookkeeping across replay attempts. If a replayable flush response is received and the retry then fails before cifs_send_recv() stores a replacement response, flush_exit will free the stale response pointer a second time. Reinitialize resp_buftype and rsp_iov at the top of the replay loop so cleanup only acts on response state produced by the current attempt. This fixes a double-free without changing replay handling for successful requests.
CVE-2026-64067CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: netfs: Fix missing barriers when accessing stream->subrequests locklessly The list of subrequests attached to stream->subrequests is accessed without locks by netfs_collect_read_results() and netfs_collect_write_results(), and then they access subreq->flags without taking a barrier after getting the subreq pointer from the list. Relatedly, the functions that build the list don't use any sort of write barrier when constructing the list to make sure that the NETFS_SREQ_IN_PROGRESS flag is perceived to be set first if no lock is taken. Fix this by: (1) Add a new list_add_tail_release() function that uses a release barrier to set the pointer to the new member of the list. (2) Add a new list_first_entry_or_null_acquire() function that uses an acquire barrier to read the pointer to the first member in a list (or return NULL). (3) Use list_add_tail_release() when adding a subreq to ->subrequests. (4) Use list_first_entry_or_null_acquire() when initially accessing the front of the list (when an item is removed, the pointer to the new front iterm is obtained under the same lock).

References

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