CVE-2022-49049 is a vulnerability in the Linux kernel related to the memfd_secret subsystem, which is designed to provide secure memory regions that are not directly mapped via the kernel's direct memory map. The issue arises when an existing memfd_secret file descriptor is grown using the ftruncate system call. Normally, growing a file descriptor with ftruncate triggers kernel functions that zero out the newly allocated memory via the direct map using page_address() and memset(). However, memfd_secret pages are deliberately unmapped from the direct map (using set_direct_map_invalid_noflush()) to enhance security, making the address returned by page_address() invalid for memset operations. This mismatch causes a kernel panic due to a page fault when the kernel attempts to zero the new memory region during the resize operation. The panic manifests as a supervisor write access fault in kernel mode, leading to a system crash. The patch implemented avoids the panic by introducing a custom setattr handler for memfd_secret that rejects attempts to grow the memfd_secret file with an EINVAL error, effectively disabling resizing for now. While growing memfd_secret could be supported with more extensive changes, the fix prioritizes stability in current kernel versions. This vulnerability is triggered by a relatively simple sequence of operations involving memfd_secret creation, memory mapping, unmapping, and then resizing with ftruncate, making it reproducible. There are no known exploits in the wild, and no CVSS score has been assigned yet. The vulnerability affects Linux kernel versions containing the affected commit hashes referenced, and the patch is included in stable kernel updates.

For European organizations relying on Linux-based systems, this vulnerability could lead to unexpected kernel panics and system crashes if applications or services use memfd_secret and attempt to resize these memory regions. Such crashes could cause denial of service (DoS) conditions, impacting availability of critical systems, servers, or embedded devices running vulnerable kernels. Although memfd_secret is a specialized feature, it may be used in security-sensitive applications requiring protected memory, such as cryptographic key storage or secure enclaves. The inability to safely grow memfd_secret regions could disrupt these applications or force them to avoid resizing operations, potentially complicating development or deployment. Since the vulnerability causes a kernel panic, it affects system stability and availability rather than confidentiality or integrity directly. There is no indication that this vulnerability can be exploited for privilege escalation or arbitrary code execution. However, denial of service in critical infrastructure or cloud environments could have cascading effects on business operations. European organizations with Linux servers, especially those using custom or older kernel versions without the patch, should be aware of this risk. The lack of known exploits reduces immediate threat, but the reproducibility of the panic means attackers could induce DoS if they can trigger the vulnerable code path.

European organizations should ensure that all Linux systems are updated to kernel versions that include the patch for CVE-2022-49049. Specifically, kernel updates that implement the custom setattr handler rejecting memfd_secret resizing should be applied promptly. Systems running custom or long-term support kernels should backport the patch if official updates are not yet available. Developers and system administrators should audit applications to identify any use of memfd_secret and avoid calling ftruncate to grow these file descriptors. If resizing is necessary, alternative memory management strategies should be considered until full support for growing memfd_secret is implemented in future kernel releases. Monitoring system logs for kernel panics related to memfd_secret or ftruncate operations can help detect attempts to trigger this vulnerability. In environments where memfd_secret is not used, the risk is minimal, but kernel updates remain recommended for overall security hygiene. Additionally, implementing robust system monitoring and automated kernel update mechanisms can reduce exposure time to such vulnerabilities.