What’s Vulnerable › Vulnerabilities

CVE-2026-64257: smb: client: reject overlapping data areas in SMB2 responses

• Severity: critical (CVSS 9.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-25 · updated 2026-08-17

Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: reject overlapping data areas in SMB2 responses Commit 53b7c271f06b ("smb: client: restrict implied bcc[0] exemption to responses without data area") restricted the implied bcc[0] length exception to responses without a data area. However, the overlap handling in __smb2_calc_size() clears data_length, which can make an invalid response appear to have no data area and so qualify for the exception. Track data area overlap separately and reject such responses before applying the length compatibility exceptions.

Affected products

• Linux kernel: from 5.10.261 before 5.11; from 5.15.212 before 5.16; 7.2-rc3 — fixed in 5.11, 5.16

How to fix

Upgrade to a fixed version: Linux kernel 5.11, 5.16. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/36bfa52459e45c0d5b668de2f1c91f6dc5c67775
• https://git.kernel.org/stable/c/445ece263131780dee273d727a4d6f11934feec7
• https://git.kernel.org/stable/c/4a9d2657d3e05f6ed09c148cb127b4e58702275f
• https://git.kernel.org/stable/c/57cba95f0e97c6f6e45e6731da30aff091bd7460
• https://git.kernel.org/stable/c/8986c932905ea508d66da421eb2eb6e676ace1fe
• https://git.kernel.org/stable/c/fdafa1e68dc75045b7b617e6e7d2854950804d83

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