CVE-2026-72382 ksmbd: reject undersized DACLs before parsing ACEs
A malicious SMB client can trigger an integer underflow in the Linux kernel's ksmbd module, causing excessive memory allocation and potential denial of service.
- 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-2026-72382?
CVE-2026-72382 is a high-severity vulnerability in Linux, published on 15 Aug 2026. 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: reject undersized DACLs before parsing ACEs
parse_dacl() limits the attacker-controlled ACE count by comparing it with the number of minimal ACEs that fit in the DACL size. The DACL size field is 16 bits, but the expression subtracts sizeof(struct smb_acl). Because sizeof() is unsigned, a DACL size smaller than the ACL header underflows to a large size_t.
A malicious client can reach this with:
SMB2_SET_INFO (InfoType=SMB2_O_INFO_SECURITY) -> smb2_set_info_sec() -> set_info_sec() -> parse_sec_desc() -> parse_dacl() -> init_acl_state(..., 0xffff) -> init_acl_state(..., 0xffff) -> kmalloc_objs(..., 0xffff)
Thus a malformed security descriptor can make num_aces pass the guard and drive large temporary ACL state and pointer-array allocations.
Reject DACLs smaller than struct smb_acl before doing the subtraction, so the ACE count check cannot be bypassed by the underflow.
Which versions are affected by CVE-2026-72382?
How do I fix CVE-2026-72382?
Apply the vendor's patch.
Is CVE-2026-72382 being exploited?
There is no known exploitation of CVE-2026-72382 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-72382, DEBIAN-CVE-2026-72382, GHSA-xrhm-hwvc-w6q3, UBUNTU-CVE-2026-72382.