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CVSS 9.1 · CRITICAL

CVE-2026-64257Vulnerabilidad crítica en el cliente SMB2 del kernel de Linux

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.

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Análisis

A critical vulnerability has been identified in the Linux kernel SMB2 client. The flaw allows for the bypass of data length checks when processing crafted responses from a malicious server, which could lead to kernel-level exploitation for systems using CIFS/SMB mounts.

Roles relevantes

LinuxBackendCyberSecurityCloudDockerC

Severidad

Puntaje: 9.1(CRITICAL)
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
AV: NETWORK
AC: LOW
PR: NONE
UI: NONE
S: UNCHANGED
C: HIGH
I: NONE
A: HIGH

EPSS

Probabilidad de explotación (próx. 30 días): 0.0022 (0.2%)
Percentil: 12.0%
EPSS: 2026-07-26

Descripción técnica

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.

Publicada: 25/7/2026, 10:17:05
Última modificación: 27/7/2026, 5:16:37

Referencias

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