CVE-2022-49908 Bluetooth: L2CAP: Fix memory leak in vhci_write
A memory leak in the Linux kernel Bluetooth L2CAP subsystem allows attackers to cause a denial of service by exhausting system memory.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2022-49908?
CVE-2022-49908 is a medium-severity denial of service vulnerability in Linux kernel, published on 1 May 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: L2CAP: Fix memory leak in vhci_write
Syzkaller reports a memory leak as follows: ==================================== BUG: memory leak unreferenced object 0xffff88810d81ac00 (size 240): [...] hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: [<ffffffff838733d9>] __alloc_skb+0x1f9/0x270 net/core/skbuff.c:418 [<ffffffff833f742f>] alloc_skb include/linux/skbuff.h:1257 [inline] [<ffffffff833f742f>] bt_skb_alloc include/net/bluetooth/bluetooth.h:469 [inline] [<ffffffff833f742f>] vhci_get_user drivers/bluetooth/hci_vhci.c:391 [inline] [<ffffffff833f742f>] vhci_write+0x5f/0x230 drivers/bluetooth/hci_vhci.c:511 [<ffffffff815e398d>] call_write_iter include/linux/fs.h:2192 [inline] [<ffffffff815e398d>] new_sync_write fs/read_write.c:491 [inline] [<ffffffff815e398d>] vfs_write+0x42d/0x540 fs/read_write.c:578 [<ffffffff815e3cdd>] ksys_write+0x9d/0x160 fs/read_write.c:631 [<ffffffff845e0645>] do_syscall_x64 arch/x86/entry/common.c:50 [inline] [<ffffffff845e0645>] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 [<ffffffff84600087>] entry_SYSCALL_64_after_hwframe+0x63/0xcd ====================================
HCI core will uses hci_rx_work() to process frame, which is queued to the hdev->rx_q tail in hci_recv_frame() by HCI driver.
Yet the problem is that, HCI core may not free the skb after handling ACL data packets. To be more specific, when start fragment does not contain the L2CAP length, HCI core just copies skb into conn->rx_skb and finishes frame process in l2cap_recv_acldata(), without freeing the skb, which triggers the above memory leak.
This patch solves it by releasing the relative skb, after processing the above case in l2cap_recv_acldata().
Weakness: CWE-401
Which versions are affected by CVE-2022-49908?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2022-49908?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2022-49908 being exploited?
There is no known exploitation of CVE-2022-49908 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as DEBIAN-CVE-2022-49908, GHSA-p98w-xrc8-4w6x, UBUNTU-CVE-2022-49908.