Critical Buffer Reallocation Vulnerability in Linux Kernel (CVE-2025-21836)
Summary
CVE-2025-21836: In the Linux kernel, the following vulnerability has been resolved: io_uring/kbuf: reallocate buf lists on upgrade IORING_REGISTER_PBUF_RING can reuse an old struct io_buffer_list if it was created for legacy selected bu... Affects linux versions 6.1.106-1 – 6.9.9-1. No fix is published. How to fix ↓
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Background
The Linux kernel is the core component of many operating systems, providing essential services for hardware and software interactions. It is widely used in various distributions, including Debian. The kernel's functionality includes process management, memory management, device drivers, and system calls. This vulnerability affects the io_uring subsystem, which is designed for asynchronous I/O operations, allowing applications to perform I/O operations efficiently. The vulnerability arises from improper handling of buffer lists during upgrades, potentially leading to system instability or security issues.
Vulnerability Detail
In the Linux kernel, the io_uring subsystem has a vulnerability where the IORING_REGISTER_PBUF_RING can reuse an old struct io_buffer_list if it was created for a legacy selected buffer and has been emptied. This violates the requirement that most fields should remain stable after publication. The improper reallocation of buffer lists can lead to unexpected behavior, including potential data corruption or system crashes, as the integrity of the buffer management is compromised.
How To Fix
No fixed version is published for this vulnerability.
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Workaround
Currently, no specific workarounds have been provided for this vulnerability. It is recommended to apply the patch as soon as it becomes available.
Conclusion
CVE-2025-21836 is a critical vulnerability in the Linux kernel that affects the io_uring subsystem. Users are advised to update their systems to the latest patched versions to mitigate the risks associated with this vulnerability. Monitoring tools like Vulert can help keep your applications secure.
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FAQ
CVE-2025-21836 is a vulnerability in the Linux kernel's io_uring subsystem that involves improper handling of buffer lists, potentially leading to system instability.
This vulnerability can lead to unexpected behavior, including data corruption or system crashes, due to the improper management of buffer lists.
If you are using Debian 12 or 13, your version of the Linux kernel may be affected. It is advisable to check for updates and apply them.
You can use Vulert, which monitors and alerts in real-time for open-source vulnerabilities in your software using just a manifest file like package-lock.json.
You can use the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without requiring any signup.
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