CVE-2026-89634

Received Received - Intake

Buffer Overflow Fix in Linux Kernel SMB Client

Publication date: 2026-09-11

Last updated on: 2026-09-11

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix ALIGN() overflow in symlink_data() error context loop The check added by commit 7d9a7f1f96cd ("smb/client: fix possible infinite loop and oob read in symlink_data()") compared the post-ALIGN length against the remaining buffer, but ALIGN() itself can overflow: for ErrorDataLength near UINT32_MAX (e.g. 0xFFFFFFF9), ALIGN(x, 8) wraps to 0, so the subsequent bounds check passes, and the loop advances by zero bytes leaving 'p' pointing into stale data. Fix by checking the raw ErrorDataLength against the remaining space before applying ALIGN(), then checking again after. Since raw_len is bounded by the buffer, raw_len + 7 cannot overflow, so the second check is an exact post-alignment bounds guard.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-09-11

Last Modified

2026-09-11

Generated

2026-09-12

AI Q&A

2026-09-12

EPSS Evaluated

N/A

NVD

CVE-2026-89634

EUVD

EUVD-2026-76546

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability in the Linux kernel involves an overflow issue in the smb client component. The problem occurs in the symlink_data() function where an ALIGN() operation can wrap around to zero due to large input values near UINT32_MAX. This causes a bounds check to pass incorrectly, leading to a loop that advances by zero bytes and leaves a pointer in stale data.

Detection Guidance

This vulnerability is specific to the Linux kernel's SMB client implementation and requires kernel-level inspection. Detection involves checking if your kernel version includes the vulnerable code path. Use commands like 'uname -a' to check your kernel version and 'grep' to inspect SMB client code for the affected function. However, no direct network detection commands are provided in the context.

Impact Analysis

This vulnerability could allow an attacker to cause a denial of service or potentially execute arbitrary code by exploiting the overflow in the smb client's symlink handling. It may lead to system crashes or unauthorized access if the kernel processes malicious smb traffic.

Mitigation Strategies

Immediate mitigation involves updating your Linux kernel to a patched version that resolves the issue. Check your distribution's security advisories for kernel updates. If no patch is available, consider disabling SMB client functionality or restricting network access to SMB servers until the update is applied.

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