CVE-2026-68098

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: bound DACL dedup walk to copied ACEs

set_ntacl_dacl() can stop copying ACEs before consuming the full input DACL when size accounting overflows.

When that happens, num_aces reflects only the ACEs that were actually copied into the output DACL, but set_posix_acl_entries_dacl() still receives nt_num_aces and uses it to walk the existing ACE array during dedup.

That makes the dedup walk scan past the copied ACE array and inspect buffer tail that does not contain valid ACEs.

Split the two meanings currently carried by the NT ACE count. Pass the number of copied NT ACEs to bound the dedup walk, and preserve the original input DACL had NT ACEs state separately for the Everyone/default ACL fallback.

This keeps the dedup walk aligned with the ACEs that are actually present in the rebuilt DACL.

Weakness

The product reads data past the end, or before the beginning, of the intended buffer.

Affected Software

Potential Mitigations

• Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
• When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
• Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
• To reduce the likelihood of introducing an out-of-bounds read, ensure that you validate and ensure correct calculations for any length argument, buffer size calculation, or offset. Be especially careful of relying on a sentinel (i.e. special character such as NUL) in untrusted inputs.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/540.html

References

• https://git.kernel.org/stable/c/05aa552bd69a96e090cbd45656e18cdc46524e20
• https://git.kernel.org/stable/c/58d97fcd0bf1aee694e244cc28635b9df95b543b
• https://git.kernel.org/stable/c/6d9d7aa4a2c99c31acfa28921c30b684110cf66c
• https://git.kernel.org/stable/c/a0ebdaa79e10210d4e8ed9fe138e8f4d569719e3
• https://git.kernel.org/stable/c/b057a851129c6a084e7e393b62ca3abf6c2660bc
• https://git.kernel.org/stable/c/f1eba60db813ec28732bf18b5f0a67ebac9c3100