medium CVSS 5.5

CVE-2024-38554·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: ax25: Fix reference count leak issue of net_device There is a reference count leak issue of the object "net_device" in ax25_dev_device_down(). When the ax25 device is shutting down, the ax25_dev_device_down() drops the reference count of net_device one or zero times depending on if we goto unlock_put or not, which will cause memory leak. In order to solve the above issue, decrease the reference count of net_device after dev->ax25_ptr is set to null.

Severity
medium
Software
Kernel
Fixed in
6.9.3
Published
2024-06-19

Affected versions

From: 6.9

Until: 6.9.3

Fixed in: 6.9.3

How to fix this CVE

Update your Linux kernel to version 6.9.3 or later to patch a reference count leak in the ax25 networking subsystem that occurs during device shutdown. This memory leak can accumulate over time as ax25 devices are brought down, potentially degrading system stability. Apply the kernel update and reboot your system to activate the fix.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check your installed kernel version with `uname -r` — vulnerable versions are 6.9 through 6.9.2
  2. Step 2: Verify if ax25 (Amateur Radio AX.25) is loaded with `lsmod | grep ax25` — if not present, the attack surface is minimal but the leak still occurs during module operations
  3. Step 3: Monitor dmesg and syslog for repeated ax25 device down/up cycles with `grep -i ax25 /var/log/syslog` or `journalctl -g ax25` — excessive cycles may indicate the leak being triggered
  4. Step 4: After applying the update, confirm the new kernel version is running with `uname -r` and verify it reports 6.9.3 or newer

FAQ

What is CVE-2024-38554?

CVE-2024-38554 is a reference count leak in the Linux kernel's ax25 (Amateur Radio) network device driver. When an ax25 device shuts down, the kernel fails to properly release its reference to the underlying network device object, causing memory not to be freed and gradually consuming system memory.

Is CVE-2024-38554 being actively exploited?

No, CVE-2024-38554 is not listed in CISA's Known Exploited Vulnerabilities catalog and no public exploit code is available. However, this is a local privilege denial of service vector that requires ax25 module interaction.

What versions of Kernel are affected by CVE-2024-38554?

Linux kernel versions 6.9, 6.9.1, and 6.9.2 are vulnerable. Version 6.9.3 and all subsequent versions contain the fix.

How do I check if my server is vulnerable to CVE-2024-38554?

Run `uname -r` to check your kernel version — if it shows 6.9.0, 6.9.1, or 6.9.2, your system is vulnerable. Additionally, check if ax25 modules are present with `lsmod | grep ax25`.

Does Defensia detect CVE-2024-38554?

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-2024-38554 will appear in your dashboard with remediation steps.

Related Kernel CVEs

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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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