medium CVSS 5.5

CVE-2024-40938·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: landlock: Fix d_parent walk The WARN_ON_ONCE() in collect_domain_accesses() can be triggered when trying to link a root mount point. This cannot work in practice because this directory is mounted, but the VFS check is done after the call to security_path_link(). Do not use source directory's d_parent when the source directory is the mount point. [mic: Fix commit message]

Severity
medium
Software
Kernel
Fixed in
6.9.6
Published
2024-07-12

Affected versions

From: 6.7

Until: 6.9.6

Fixed in: 6.9.6

How to fix this CVE

Update your Linux kernel to version 6.9.6 or later to resolve a path traversal vulnerability in the Landlock security module. This fix prevents a warning condition that could be triggered during symlink operations on mount points. Apply the kernel update and reboot your system to enable the security patch.

sudo dnf update kernel

Defensia detects this vulnerability

How to check if you are affected

  1. Check installed kernel version with: uname -r (vulnerable if output is between 6.7 and 6.9.5)
  2. Verify Landlock is enabled with: grep -i landlock /boot/config-$(uname -r) (should show CONFIG_SECURITY_LANDLOCK=y)
  3. Search system logs for Landlock warnings with: sudo journalctl -b | grep -i 'collect_domain_accesses\|WARN_ON'
  4. After patching, confirm new version with: uname -r (should be 6.9.6 or later)

FAQ

What is CVE-2024-40938?

CVE-2024-40938 is a vulnerability in the Linux kernel's Landlock security module where incorrect directory parent traversal during symlink operations can trigger a kernel warning condition. This affects systems using Landlock for mandatory access control policies.

Is CVE-2024-40938 being actively exploited?

No, this vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog and has no public exploit code available.

What versions of Kernel are affected by CVE-2024-40938?

Linux kernel versions 6.7 through 6.9.5 are affected. Kernel 6.9.6 and later contain the security fix.

How do I check if my server is vulnerable to CVE-2024-40938?

Run 'uname -r' to display your kernel version. If it shows 6.7.x through 6.9.5, your system is vulnerable. Additionally, verify Landlock is compiled in with 'grep CONFIG_SECURITY_LANDLOCK /boot/config-$(uname -r)'.

Does Defensia detect CVE-2024-40938?

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-2024-40938 will appear in your dashboard with remediation steps.

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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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