CVE-2025-39946: Linux Kernel TLS Out of Bounds Write Vulnerability
Summary
CVE-2025-39946: In tls_rx_msg_size of tls_sw.c, there is a possible out of bounds write due to an incorrect bounds check. Affects :linux_kernel: versions >= :0, < :2026-03-05. Fixed in :2026-03-05. How to fix ↓
Also tracked for
The same CVE-2025-39946 is tracked separately for each ecosystem and vendor. Its fix information is the same; the package and affected versions differ.
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Background
The Linux Kernel is the core component of the Linux operating system, responsible for managing hardware resources and providing essential services to applications. It supports various functionalities, including process management, memory management, and device drivers. The TLS (Transport Layer Security) subsystem within the kernel is crucial for secure communications over networks. However, it has been found to have a vulnerability that could lead to serious security issues.
Vulnerability Detail
In the tls_rx_msg_size function of tls_sw.c, there exists a potential out of bounds write due to an incorrect bounds check. This flaw could allow an attacker to escalate privileges locally without requiring additional execution privileges. The vulnerability arises from improper validation of input sizes, which can lead to memory corruption and unauthorized access to sensitive data or system functions.
How To Fix
Minimum fixed version
:2026-03-05
This is the first release that contains the fix.
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Workaround
Currently, there are no specific workarounds mentioned for this vulnerability. It is strongly recommended to apply the patches as soon as they are available to mitigate the risk.
Conclusion
The CVE-2025-39946 vulnerability in the Linux Kernel's TLS subsystem poses a significant risk due to its potential for local privilege escalation. It is imperative to apply the available patches to secure your system against this threat. Utilizing tools like Vulert can help monitor for such vulnerabilities effectively.
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FAQ
CVE-2025-39946 is a vulnerability in the Linux Kernel's TLS subsystem that allows for an out of bounds write, potentially leading to local privilege escalation.
You can use the Vulert platform to monitor and alert for open-source vulnerabilities in your software. Visit Vulert Scanner to check if your application is affected without requiring any signup.
Exploitation of this vulnerability could allow an attacker to gain elevated privileges on the system, potentially leading to unauthorized access to sensitive data or system control.
No, user interaction is not needed for exploitation of this vulnerability, making it particularly dangerous.
While there are no specific workarounds, it is crucial to prioritize updating your kernel to the patched version as soon as possible to mitigate risks.
References
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