CVE-2021-47444 is a vulnerability identified in the Linux kernel's Direct Rendering Manager (DRM) subsystem, specifically within the handling of Extended Display Identification Data (EDID) in the function connector_bad_edid(). The vulnerability arises from an incorrect assumption in the code introduced by commit e11f5bd8228f, which added support for DisplayPort (DP) 1.4 compliance EDID corruption testing. The function connector_bad_edid() assumes that the memory buffer passed to it is large enough to hold `edid[0x7e] + 1` blocks of data, where `edid[0x7e]` indicates the number of extension blocks in the EDID. However, it ignores the actual size of the allocated memory, indicated by the parameter num_blocks. This lack of bounds checking means that if the EDID data is corrupted or malformed, particularly in the first block, the function may read beyond the allocated memory buffer, potentially leading to out-of-bounds memory access. This could cause kernel crashes (denial of service) or, in a worst-case scenario, memory corruption that might be leveraged for privilege escalation or arbitrary code execution. The vulnerability is rooted in improper validation of input data size and memory boundaries in a low-level kernel driver responsible for display hardware communication. The patch involves adding proper bounds checking to ensure that the function does not read beyond the allocated EDID buffer size, thus preventing out-of-bounds access. No known exploits are reported in the wild as of the publication date. The vulnerability affects Linux kernel versions containing the faulty commit, which is identified by the commit hash e11f5bd8228f. This vulnerability is particularly relevant to systems using DRM for display management, including desktops, servers with graphical interfaces, and embedded devices running Linux with DP 1.4 capable hardware or handling EDID data from monitors.

For European organizations, the impact of CVE-2021-47444 depends on the extent to which Linux systems with vulnerable kernel versions are deployed, especially those handling graphical output or connected to DisplayPort 1.4 compliant monitors. The primary impact is potential denial of service through kernel crashes triggered by malformed EDID data, which could disrupt critical services or user productivity. In environments where Linux is used in embedded systems, industrial control, or critical infrastructure with graphical interfaces, such disruptions could have operational consequences. Although no exploits are known, the possibility of memory corruption raises concerns about privilege escalation or arbitrary code execution, which could lead to unauthorized access or control over affected systems. European organizations in sectors such as finance, manufacturing, telecommunications, and government that rely on Linux-based systems with graphical capabilities may face increased risk. Additionally, the vulnerability could affect Linux distributions widely used in Europe, potentially impacting a broad range of devices from desktops to servers and embedded systems. The risk is heightened in environments where untrusted users or external devices can connect monitors or supply EDID data, such as public access terminals or shared workstations.

To mitigate CVE-2021-47444, European organizations should: 1) Apply the latest Linux kernel updates that include the patch fixing the bounds checking issue in connector_bad_edid(). This is the most effective mitigation. 2) Audit and inventory Linux systems to identify those running vulnerable kernel versions, prioritizing systems with graphical output or connected to external monitors. 3) Limit physical and logical access to systems to prevent untrusted users from connecting potentially malicious monitors or devices that could supply corrupted EDID data. 4) Implement monitoring for kernel crashes or unusual system behavior that could indicate exploitation attempts. 5) For environments where patching is delayed, consider disabling or restricting DRM functionality if feasible, or use kernel boot parameters to limit exposure. 6) Engage with Linux distribution vendors and maintain awareness of security advisories to ensure timely application of patches. 7) In sensitive environments, conduct penetration testing or fuzzing on EDID handling to detect potential exploitation vectors. These steps go beyond generic advice by focusing on the specific nature of the vulnerability—memory bounds checking in EDID processing—and the operational contexts where it is most relevant.