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CVE-2025-40084: ksmbd: transport_ipc: validate payload size before reading handle

• Severity: high (CVSS 7.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-10-29 · updated 2026-10-19

Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: transport_ipc: validate payload size before reading handle handle_response() dereferences the payload as a 4-byte handle without verifying that the declared payload size is at least 4 bytes. A malformed or truncated message from ksmbd.mountd can lead to a 4-byte read past the declared payload size. Validate the size before dereferencing. This is a minimal fix to guard the initial handle read.

Affected products

• Linux kernel: 5.15 — fixed in 6.18

How to fix

Upgrade to a fixed version: Linux kernel 6.18. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/2dc125f5da134c0915a840b62565c60a595673dd
• https://git.kernel.org/stable/c/6f40e50ceb99fc8ef37e5c56e2ec1d162733fef0
• https://git.kernel.org/stable/c/867ffd9d67285612da3f0498ca618297f8e41f01
• https://git.kernel.org/stable/c/898d527ed94c19980a4d848f10057f1fed578ffb
• https://git.kernel.org/stable/c/a02e432d5130da4c723aabe1205bac805889fdb2

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