CVE-2026-23230 smb: client: split cached_fid bitfields to avoid shared-byte RMW races
Concurrent updates to SMB client cached file ID flags can cause race conditions, potentially leading to inconsistent state or undefined behavior.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-23230?
CVE-2026-23230 is a high-severity vulnerability in Linux kernel, published on 18 Feb 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
In the Linux kernel, the following vulnerability has been resolved:
smb: client: split cached_fid bitfields to avoid shared-byte RMW races
is_open, has_lease and on_list are stored in the same bitfield byte in struct cached_fid but are updated in different code paths that may run concurrently. Bitfield assignments generate byte read–modify–write operations (e.g. `orb $mask, addr` on x86_64), so updating one flag can restore stale values of the others.
A possible interleaving is: CPU1: load old byte (has_lease=1, on_list=1) CPU2: clear both flags (store 0) CPU1: RMW store (old | IS_OPEN) -> reintroduces cleared bits
To avoid this class of races, convert these flags to separate bool fields.
Weakness: CWE-362
Which versions are affected by CVE-2026-23230?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-23230?
Apply the vendor's patch.
Is CVE-2026-23230 being exploited?
There is no known exploitation of CVE-2026-23230 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-23230, DEBIAN-CVE-2026-23230, GHSA-p68h-c56f-p3v6, ROOT-OS-DEBIAN-11-CVE-2026-23230, ROOT-OS-DEBIAN-12-CVE-2026-23230, ROOT-OS-UBUNTU-2404-CVE-2026-23230 and 1 more.