CVE-2025-21994 ksmbd: fix incorrect validation for num_aces field of smb_acl
An integer overflow in the Linux kernel's ksmbd module allows attackers to cause a denial of service via crafted SMB requests.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-21994?
CVE-2025-21994 is a high-severity vulnerability in Linux kernel, published on 2 Apr 2025. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: fix incorrect validation for num_aces field of smb_acl
parse_dcal() validate num_aces to allocate posix_ace_state_array.
if (num_aces > ULONG_MAX / sizeof(struct smb_ace *))
It is an incorrect validation that we can create an array of size ULONG_MAX. smb_acl has ->size field to calculate actual number of aces in request buffer size. Use this to check invalid num_aces.
Which versions are affected by CVE-2025-21994?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-21994?
Apply the vendor's patch.
Is CVE-2025-21994 being exploited?
There is no known exploitation of CVE-2025-21994 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-21994, DEBIAN-CVE-2025-21994, GHSA-pcv3-r2v8-4964, ROOT-OS-UBUNTU-2404-CVE-2025-21994, UBUNTU-CVE-2025-21994.