CVE-2021-47081 is a use-after-free (UAF) vulnerability identified in the Linux kernel, specifically within the habanalabs/gaudi driver component responsible for managing device memory operations. The vulnerability arises in the function gaudi_memset_device_memory, where a control block (cb) is obtained via hl_cb_kernel_create() with two reference counts. If the function hl_cs_allocate_job() fails, the code path leads to the release_cb branch, where one reference count of cb is decremented by hl_cb_put(cb). If another thread concurrently decrements the remaining reference, the cb object may be freed prematurely. Subsequently, the code attempts to access cb->id, resulting in a use-after-free condition. This can lead to undefined behavior including potential memory corruption, kernel crashes, or escalation of privileges if exploited. The patch introduced mitigates this by storing the cb->id value in a separate variable before calling hl_cb_put(cb), thereby avoiding dereferencing a freed pointer. This vulnerability is rooted in improper reference counting and concurrency handling within the driver code, which is critical in kernel space due to the high privileges and potential impact on system stability and security.

For European organizations, the impact of CVE-2021-47081 depends largely on the deployment of Linux systems utilizing the habanalabs/gaudi driver, which is associated with Habana Labs AI processors. Organizations involved in AI research, data centers, cloud service providers, and enterprises leveraging AI acceleration hardware could be affected. Exploitation of this vulnerability could allow attackers to cause kernel crashes leading to denial of service or potentially execute arbitrary code with kernel privileges, compromising system confidentiality, integrity, and availability. This poses significant risks to critical infrastructure, research institutions, and enterprises relying on AI workloads. Additionally, the concurrency nature of the bug could be exploited in multi-threaded environments common in server and cloud deployments. Although no known exploits are currently reported in the wild, the vulnerability’s presence in the Linux kernel—a widely used OS in Europe—means that unpatched systems remain at risk. The impact is heightened in environments where Habana Labs hardware is integrated, especially in sectors with stringent security requirements such as finance, healthcare, and government.

Mitigation requires applying the official patch that addresses the use-after-free by safely handling the cb reference counting and access. European organizations should: 1) Identify all Linux systems using the habanalabs/gaudi driver, particularly those with Habana Labs AI accelerators. 2) Update the Linux kernel to a version that includes the fix for CVE-2021-47081 as soon as it becomes available from their Linux distribution vendor or directly from the kernel source. 3) In environments where immediate patching is not feasible, implement strict access controls and monitoring around systems running affected drivers to detect anomalous behavior indicative of exploitation attempts. 4) Conduct thorough testing of AI workloads post-patch to ensure stability and performance are maintained. 5) Collaborate with hardware vendors to receive timely updates and guidance. 6) Employ kernel hardening techniques such as Kernel Address Space Layout Randomization (KASLR) and Control Flow Integrity (CFI) to reduce exploitation likelihood. 7) Maintain robust incident response plans to quickly address potential exploitation.