medium CVSS 6.5

CVE-2024-36968·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: Fix div-by-zero in l2cap_le_flowctl_init() l2cap_le_flowctl_init() can cause both div-by-zero and an integer overflow since hdev->le_mtu may not fall in the valid range. Move MTU from hci_dev to hci_conn to validate MTU and stop the connection process earlier if MTU is invalid. Also, add a missing validation in read_buffer_size() and make it return an error value if the validation fails. Now hci_conn_add() returns ERR_PTR() as it can fail due to the both a kzalloc failure and invalid MTU value. divide error: 0000 [#1] PREEMPT SMP KASAN NOPTI CPU: 0 PID: 67 Comm: kworker/u5:0 Tainted: G W 6.9.0-rc5+ #20 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 Workqueue: hci0 hci_rx_work RIP: 0010:l2cap_le_flowctl_init+0x19e/0x3f0 net/bluetooth/l2cap_core.c:547 Code: e8 17 17 0c 00 66 41 89 9f 84 00 00 00 bf 01 00 00 00 41 b8 02 00 00 00 4c 89 fe 4c 89 e2 89 d9 e8 27 17 0c 00 44 89 f0 31 d2 <66> f7 f3 89 c3 ff c3 4d 8d b7 88 00 00 00 4c 89 f0 48 c1 e8 03 42 RSP: 0018:ffff88810bc0f858 EFLAGS: 00010246 RAX: 00000000000002a0 RBX: 0000000000000000 RCX: dffffc0000000000 RDX: 0000000000000000 RSI: ffff88810bc0f7c0 RDI: ffffc90002dcb66f RBP: ffff88810bc0f880 R08: aa69db2dda70ff01 R09: 0000ffaaaaaaaaaa R10: 0084000000ffaaaa R11: 0000000000000000 R12: ffff88810d65a084 R13: dffffc0000000000 R14: 00000000000002a0 R15: ffff88810d65a000 FS: 0000000000000000(0000) GS:ffff88811ac00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020000100 CR3: 0000000103268003 CR4: 0000000000770ef0 PKRU: 55555554 Call Trace: <TASK> l2cap_le_connect_req net/bluetooth/l2cap_core.c:4902 [inline] l2cap_le_sig_cmd net/bluetooth/l2cap_core.c:5420 [inline] l2cap_le_sig_channel net/bluetooth/l2cap_core.c:5486 [inline] l2cap_recv_frame+0xe59d/0x11710 net/bluetooth/l2cap_core.c:6809 l2cap_recv_acldata+0x544/0x10a0 net/bluetooth/l2cap_core.c:7506 hci_acldata_packet net/bluetooth/hci_core.c:3939 [inline] hci_rx_work+0x5e5/0xb20 net/bluetooth/hci_core.c:4176 process_one_work kernel/workqueue.c:3254 [inline] process_scheduled_works+0x90f/0x1530 kernel/workqueue.c:3335 worker_thread+0x926/0xe70 kernel/workqueue.c:3416 kthread+0x2e3/0x380 kernel/kthread.c:388 ret_from_fork+0x5c/0x90 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 </TASK> Modules linked in: ---[ end trace 0000000000000000 ]---

Severity
medium
Software
Kernel
Fixed in
6.9.2
Published
2024-06-08

Affected versions

From: 6.9

Until: 6.9.2

Fixed in: 6.9.2

How to fix this CVE

Update your Linux kernel to version 6.9.2 or later to resolve a division-by-zero vulnerability in Bluetooth L2CAP flow control initialization. This flaw occurs when an invalid MTU (Maximum Transmission Unit) value is processed during Bluetooth connection setup, potentially causing kernel crashes. Applying this patch validates MTU values early in the connection process and prevents the arithmetic error.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Check installed kernel version: uname -r (should be 6.9.2 or later to be patched)
  2. Verify Bluetooth subsystem is enabled: grep -i bluetooth /boot/config-$(uname -r)
  3. Monitor for div-by-zero errors in kernel logs: sudo dmesg | grep -i 'divide error\|l2cap_le_flowctl'
  4. After patching, confirm the new kernel is active: uname -r should show version 6.9.2 or higher

FAQ

What is CVE-2024-36968?

A division-by-zero vulnerability in the Linux kernel's Bluetooth L2CAP subsystem that occurs when an invalid MTU value is not properly validated during connection initialization, potentially triggering a kernel panic on affected systems.

Is CVE-2024-36968 being actively exploited?

No, this vulnerability is not listed on the CISA Known Exploited Vulnerabilities (KEV) catalog and no public exploits are currently available, though it can be triggered by malicious or misconfigured Bluetooth devices.

What versions of Kernel are affected by CVE-2024-36968?

Linux kernel versions 6.9 through 6.9.1 are vulnerable. The fix was released in kernel version 6.9.2.

How do I check if my server is vulnerable to CVE-2024-36968?

Run 'uname -r' to check your kernel version; if it is 6.9, 6.9.1, or similar (check the full version string), you are likely vulnerable. For precise vulnerability assessment, check your distribution's security advisories.

Does Defensia detect CVE-2024-36968?

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-2024-36968 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.
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References

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