CVE-2026-68368 usb: gadget: f_ncm: validate datagram bounds in ncm_unwrap_ntb()
A malicious USB host can trigger out-of-bounds memory reads in the Linux kernel NCM gadget driver, potentially leaking kernel memory or executing code.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-68368?
CVE-2026-68368 is a memory corruption vulnerability in Linux, published on 10 Aug 2026. 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:
usb: gadget: f_ncm: validate datagram bounds in ncm_unwrap_ntb()
When unpacking host-supplied NTBs, ncm_unwrap_ntb() checks datagram length against frame_max but does not verify that the datagram fits within the declared block length. Additionally, when decoding multiple NTBs from a single socket buffer, subsequent block lengths are not checked against the actual remaining buffer data.
With these checks missing, a malicious USB host can specify datagram offsets and lengths that point beyond the block, or supply secondary NTB headers declaring lengths larger than the buffer. skb_put_data() then copies adjacent kernel memory from skb_shared_info into the network skb.
Fix this by verifying that sufficient buffer space remains for the NTB header before parsing, handling zero-length block declarations, ensuring that block lengths never exceed the remaining buffer space, and verifying that each datagram payload stays strictly within the block boundary.
Which versions are affected by CVE-2026-68368?
How do I fix CVE-2026-68368?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-68368 being exploited?
There is no known exploitation of CVE-2026-68368 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-68368, DEBIAN-CVE-2026-68368, GHSA-jmw8-f562-3f2g, UBUNTU-CVE-2026-68368.