CVE-2026-64257

Analyzed Analyzed - Analysis Complete

SMB2 Client Data Overlap Handling Flaw in Linux Kernel

Publication date: 2026-07-25

Last updated on: 2026-08-12

Assigner: kernel.org

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.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-07-25

Last Modified

2026-08-12

Generated

2026-08-14

AI Q&A

2026-07-25

EPSS Evaluated

2026-08-13

NVD

CVE-2026-64257

EUVD

EUVD-2026-48969

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	7.2
linux	linux_kernel	From 5.10.261 (inc) to 5.11 (exc)
linux	linux_kernel	From 5.15.212 (inc) to 5.16 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability in the Linux kernel involves a flaw in the SMB2 protocol client implementation. It allows an attacker to craft malicious SMB2 responses that bypass security checks by exploiting an overlap in data areas. The issue arises because the kernel incorrectly clears data length information, making invalid responses appear valid.

Detection Guidance

This vulnerability involves SMB2 response handling in the Linux kernel. Detection requires checking for malformed SMB2 responses with overlapping data areas. Monitor kernel logs for SMB-related errors or use network traffic analysis tools like Wireshark to inspect SMB2 packets for invalid data structures. No specific commands are provided in the context.

Impact Analysis

This vulnerability could allow an attacker to send specially crafted SMB2 responses to a vulnerable system, potentially leading to unauthorized access, data corruption, or denial of service. Systems using the Linux kernel with SMB2 client functionality are at risk.

Compliance Impact

This vulnerability affects compliance with standards like GDPR and HIPAA by potentially allowing unauthorized data access or manipulation through malformed SMB2 responses. Exploiting this flaw could lead to data breaches or integrity violations, which are critical concerns under GDPR and HIPAA.

Mitigation Strategies

Update the Linux kernel to a version that includes the fix for this vulnerability. Monitor vendor advisories for kernel updates and apply them promptly.

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