CVE-2021-47655 is a vulnerability identified in the Linux kernel's media subsystem, specifically within the Venus video decoder (vdec) component. The issue arises from a potential memory leak in the function venus_helper_alloc_dpb_bufs(). This function is responsible for allocating buffers used during video decoding. The vulnerability occurs because the function allows an early return on an error path after calling ida_alloc_min(), which allocates an ID but does not release previously allocated buffers if an error occurs. Additionally, the direct call to kfree() (kernel free) for releasing allocated memory is misplaced within the error handling code for dma_alloc_attrs(), leading to some allocations not being freed on all error paths. This results in a resource leak where memory buffers remain allocated and unreleased, potentially leading to increased memory consumption over time. The issue was identified and fixed by moving the kfree() call to a common failure path, ensuring all allocated resources are properly released regardless of the error condition. The vulnerability does not appear to have any known exploits in the wild, and no CVSS score has been assigned. It primarily affects specific Linux kernel versions identified by their commit hashes. The flaw is a resource management bug rather than a direct code execution or privilege escalation vulnerability, but it can degrade system stability or availability if exploited or triggered repeatedly.

For European organizations, the impact of CVE-2021-47655 is primarily related to system stability and availability rather than direct compromise of confidentiality or integrity. Systems running vulnerable Linux kernel versions with the Venus video decoder enabled could experience memory leaks that, over time, may lead to resource exhaustion. This can cause degraded performance, system slowdowns, or even crashes, particularly on servers or embedded devices processing video streams or media content. Organizations relying on Linux-based infrastructure for media processing, streaming services, or embedded systems in telecommunications or industrial environments could be affected. Although no active exploits are known, persistent triggering of this vulnerability could be used as a denial-of-service vector. The vulnerability does not require user interaction or authentication to be triggered if the vulnerable code path is reachable, which could increase risk in exposed environments. However, the impact is limited to resource leakage rather than direct compromise, so the threat is moderate in severity. European organizations with critical media processing workloads or embedded Linux devices should be aware and apply patches promptly to avoid potential service disruptions.

To mitigate CVE-2021-47655, European organizations should: 1) Identify and inventory Linux systems running kernel versions affected by this vulnerability, focusing on those with the Venus video decoder enabled. 2) Apply the official Linux kernel patches that fix the memory leak by ensuring all allocated buffers are freed on error paths. If official patches are not yet available, consider upgrading to a newer kernel version where the issue is resolved. 3) Monitor system memory usage and logs for signs of abnormal memory consumption or resource exhaustion related to media decoding processes. 4) For embedded or specialized devices, coordinate with vendors to obtain firmware or kernel updates addressing this issue. 5) Limit exposure of vulnerable systems to untrusted inputs or network access that could trigger the vulnerable code path. 6) Implement resource limits and watchdog mechanisms to detect and recover from potential memory leaks or crashes. These steps go beyond generic advice by emphasizing targeted patching, monitoring, and vendor coordination specific to the media subsystem and Venus decoder component.