Out-of-Bounds Vulnerability in Linux Kernel's ksmbd Package
Summary
CVE-2025-21946: In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix out-of-bounds in parse_sec_desc() If osidoffset, gsidoffset and dacloffset could be greater than smb_ntsd struct size. Affects linux versions 6.1.106-1 – 6.9.9-1. No fix is published. How to fix ↓
Check if this vulnerability affects your application
Upload a manifest or SBOM and we'll show whether you're affected, plus every other risky package in the same scan.
No signup required · Results in about 60 seconds
Habilume
Habit tracker with a companion that grows with you
Complete habits, earn Lume Points, and watch your Lume grow as you stay consistent.
Background
The Linux kernel is a core component of many operating systems, providing essential services for hardware and software interactions. The ksmbd module enables SMB (Server Message Block) protocol support, allowing file sharing and printer services over a network. This module is crucial for systems that require interoperability with Windows environments. However, vulnerabilities in the kernel can lead to severe security risks, including unauthorized access and system crashes.
Vulnerability Detail
The vulnerability identified as CVE-2025-21946 arises from improper validation of offsets in the ksmbd module. Specifically, the osidoffset, gsidoffset, and dacloffset can exceed the size of the smb_ntsd structure, leading to slab-out-of-bounds conditions. This flaw can be exploited to manipulate memory, potentially allowing attackers to execute arbitrary code or crash the system. The vulnerability underscores the importance of validating input sizes against expected limits, particularly in security-sensitive components like the kernel.
How To Fix
No fixed version is published for this vulnerability.
Tip — Not sure whether your app is affected? Vulert can check the versions your app actually runs. Scan free →
Workaround
Currently, no specific workarounds have been provided for this vulnerability. However, it is advisable to limit access to the ksmbd service and monitor system logs for any unusual activity until the system can be updated.
Conclusion
CVE-2025-21946 represents a significant security risk within the Linux kernel's ksmbd module, necessitating prompt attention from system administrators. Updating to the patched version is crucial to mitigate potential exploitation. Regular monitoring and security practices should be employed to safeguard systems against such vulnerabilities.
See every vulnerability recorded for linux →
FAQ
CVE-2025-21946 is a vulnerability in the Linux kernel's ksmbd module that can lead to out-of-bounds memory access.
Exploitation of this vulnerability can allow attackers to manipulate memory, potentially leading to unauthorized access or system crashes.
Versions of the Linux kernel in Debian 11, 12, and 13 are affected, with specific patches available for Debian 13.
You can use the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without any signup.
If immediate updates are not possible, limit access to the ksmbd service and monitor your system for any suspicious activity.
Related vulnerabilities
Recent vulnerabilities recorded for linux.
Habilume
Habit tracker with a companion that grows with you
Complete habits, earn Lume Points, and watch your Lume grow as you stay consistent.
