CVE-2026-23220 ksmbd: fix infinite loop caused by next_smb2_rcv_hdr_off reset in error paths
A flaw in the Linux kernel ksmbd module allows remote attackers to cause a denial of service via an infinite loop triggered by failed signature verification.
- 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-2026-23220?
CVE-2026-23220 is a medium-severity denial of service vulnerability in Linux kernel, published on 18 Feb 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:
ksmbd: fix infinite loop caused by next_smb2_rcv_hdr_off reset in error paths
The problem occurs when a signed request fails smb2 signature verification check. In __process_request(), if check_sign_req() returns an error, set_smb2_rsp_status(work, STATUS_ACCESS_DENIED) is called. set_smb2_rsp_status() set work->next_smb2_rcv_hdr_off as zero. By resetting next_smb2_rcv_hdr_off to zero, the pointer to the next command in the chain is lost. Consequently, is_chained_smb2_message() continues to point to the same request header instead of advancing. If the header's NextCommand field is non-zero, the function returns true, causing __handle_ksmbd_work() to repeatedly process the same failed request in an infinite loop. This results in the kernel log being flooded with "bad smb2 signature" messages and high CPU usage.
This patch fixes the issue by changing the return value from SERVER_HANDLER_CONTINUE to SERVER_HANDLER_ABORT. This ensures that the processing loop terminates immediately rather than attempting to continue from an invalidated offset.
Weakness: CWE-835
Which versions are affected by CVE-2026-23220?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-23220?
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-2026-23220 being exploited?
There is no known exploitation of CVE-2026-23220 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-23220, DEBIAN-CVE-2026-23220, GHSA-9wwr-2jh3-482p, ROOT-OS-DEBIAN-12-CVE-2026-23220, ROOT-OS-UBUNTU-2204-CVE-2026-23220, ROOT-OS-UBUNTU-2404-CVE-2026-23220 and 1 more.