CVE-2025-40016 media: uvcvideo: Mark invalid entities with id UVC_INVALID_ENTITY_ID

What is CVE-2025-40016?

CVE-2025-40016 is a denial of service vulnerability in Linux, published on 20 Oct 2025. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

Official description

In the Linux kernel, the following vulnerability has been resolved:

media: uvcvideo: Mark invalid entities with id UVC_INVALID_ENTITY_ID

Per UVC 1.1+ specification 3.7.2, units and terminals must have a non-zero unique ID.

``` Each Unit and Terminal within the video function is assigned a unique identification number, the Unit ID (UID) or Terminal ID (TID), contained in the bUnitID or bTerminalID field of the descriptor. The value 0x00 is reserved for undefined ID, ```

If we add a new entity with id 0 or a duplicated ID, it will be marked as UVC_INVALID_ENTITY_ID.

In a previous attempt commit 3dd075fe8ebb ("media: uvcvideo: Require entities to have a non-zero unique ID"), we ignored all the invalid units, this broke a lot of non-compatible cameras. Hopefully we are more lucky this time.

This also prevents some syzkaller reproducers from triggering warnings due to a chain of entities referring to themselves. In one particular case, an Output Unit is connected to an Input Unit, both with the same ID of 1. But when looking up for the source ID of the Output Unit, that same entity is found instead of the input entity, which leads to such warnings.

In another case, a backward chain was considered finished as the source ID was 0. Later on, that entity was found, but its pads were not valid.

Here is a sample stack trace for one of those cases.

[ 20.650953] usb 1-1: new high-speed USB device number 2 using dummy_hcd [ 20.830206] usb 1-1: Using ep0 maxpacket: 8 [ 20.833501] usb 1-1: config 0 descriptor?? [ 21.038518] usb 1-1: string descriptor 0 read error: -71 [ 21.038893] usb 1-1: Found UVC 0.00 device <unnamed> (2833:0201) [ 21.039299] uvcvideo 1-1:0.0: Entity type for entity Output 1 was not initialized! [ 21.041583] uvcvideo 1-1:0.0: Entity type for entity Input 1 was not initialized! [ 21.042218] ------------[ cut here ]------------ [ 21.042536] WARNING: CPU: 0 PID: 9 at drivers/media/mc/mc-entity.c:1147 media_create_pad_link+0x2c4/0x2e0 [ 21.043195] Modules linked in: [ 21.043535] CPU: 0 UID: 0 PID: 9 Comm: kworker/0:1 Not tainted 6.11.0-rc7-00030-g3480e43aeccf #444 [ 21.044101] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014 [ 21.044639] Workqueue: usb_hub_wq hub_event [ 21.045100] RIP: 0010:media_create_pad_link+0x2c4/0x2e0 [ 21.045508] Code: fe e8 20 01 00 00 b8 f4 ff ff ff 48 83 c4 30 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc 0f 0b eb e9 0f 0b eb 0a 0f 0b eb 06 <0f> 0b eb 02 0f 0b b8 ea ff ff ff eb d4 66 2e 0f 1f 84 00 00 00 00 [ 21.046801] RSP: 0018:ffffc9000004b318 EFLAGS: 00010246 [ 21.047227] RAX: ffff888004e5d458 RBX: 0000000000000000 RCX: ffffffff818fccf1 [ 21.047719] RDX: 000000000000007b RSI: 0000000000000000 RDI: ffff888004313290 [ 21.048241] RBP: ffff888004313290 R08: 0001ffffffffffff R09: 0000000000000000 [ 21.048701] R10: 0000000000000013 R11: 0001888004313290 R12: 0000000000000003 [ 21.049138] R13: ffff888004313080 R14: ffff888004313080 R15: 0000000000000000 [ 21.049648] FS: 0000000000000000(0000) GS:ffff88803ec00000(0000) knlGS:0000000000000000 [ 21.050271] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 21.050688] CR2: 0000592cc27635b0 CR3: 000000000431c000 CR4: 0000000000750ef0 [ 21.051136] PKRU: 55555554 [ 21.051331] Call Trace: [ 21.051480] <TASK> [ 21.051611] ? __warn+0xc4/0x210 [ 21.051861] ? media_create_pad_link+0x2c4/0x2e0 [ 21.052252] ? report_bug+0x11b/0x1a0 [ 21.052540] ? trace_hardirqs_on+0x31/0x40 [ 21.052901] ? handle_bug+0x3d/0x70 [ 21.053197] ? exc_invalid_op+0x1a/0x50 [ 21.053511] ? asm_exc_invalid_op+0x1a/0x20 [ 21.053924] ? media_create_pad_link+0x91/0x2e0 [ 21.054364] ? media_create_pad_link+0x2c4/0x2e0 [ 21.054834] ? media_create_pad_link+0x91/0x2e0 [ 21.055131] ? _raw_spin_unlock+0x1e/0x40 [ 21.055441] ? __v4l2_device_register_subdev+0x202/0x210 [ 21.055837] uvc_mc_register_entities+0x358/0x400 [ 21.056144] uvc_register_chains+0x1 ---truncated---

Which versions are affected by CVE-2025-40016?

How do I fix CVE-2025-40016?

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-2025-40016 being exploited?

There is no known exploitation of CVE-2025-40016 in the wild and no public exploit code.

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-68595, BELL-CVE-2025-40016, DEBIAN-CVE-2025-40016, GHSA-6jvm-59q4-2x6g, ROOT-OS-DEBIAN-11-CVE-2025-40016, ROOT-OS-DEBIAN-12-CVE-2025-40016 and 4 more.