CVE-2026-89743 misc: nsm: bound the device-reported response length
A malicious NSM device can trigger an out-of-bounds read in the Linux kernel, disclosing adjacent kernel heap memory to user space.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-89743?
CVE-2026-89743 is a high-severity vulnerability in Linux, published on 11 Sep 2026. 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:
misc: nsm: bound the device-reported response length
nsm_sendrecv_msg_locked() stores the virtqueue used-ring length reported by the NSM device into msg->resp.len without bounding it to the response buffer. A malicious or buggy backend can report a length larger than the response buffer; parse_resp_raw() then copies that many bytes out of the fixed buffer to user space, disclosing adjacent kernel heap (an out-of-bounds read). The request path already floors its length in fill_req_raw(); the response path lacks the symmetric check.
Clamp the stored length to the size of the response buffer. Well-behaved devices report no more than the posted buffer size, so conforming traffic is unaffected.
Which versions are affected by CVE-2026-89743?
How do I fix CVE-2026-89743?
Apply the vendor's patch.
Is CVE-2026-89743 being exploited?
There is no known exploitation of CVE-2026-89743 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-89743, DEBIAN-CVE-2026-89743, GHSA-ggmc-fhxw-v94j, UBUNTU-CVE-2026-89743.