CVE-2023-52979 is a vulnerability identified in the Linux kernel's handling of the SquashFS filesystem, specifically within the function squashfs_read_xattr_id_table. SquashFS is a compressed read-only filesystem commonly used in embedded systems, live Linux distributions, and container environments. The vulnerability arises when mounting a corrupted SquashFS filesystem image. A signed integer pointer '*xattr_ids' can become negative, which leads to incorrect calculations of the 'len' and 'indexes' variables. These miscalculations can cause either a null pointer dereference in the function copy_bio_to_actor() or out-of-bounds memory accesses during subsequent sanity checks in squashfs_read_xattr_id_table(). Both outcomes can lead to kernel crashes (denial of service) or potentially exploitable memory corruption. The flaw was discovered by the Linux Verification Center using the Syzkaller fuzzing tool, indicating a rigorous automated testing process. The vulnerability affects multiple Linux kernel versions identified by specific commit hashes, and no CVSS score has been assigned yet. There are no known exploits in the wild at the time of publication. The root cause is insufficient validation of filesystem metadata when processing extended attributes (xattrs) in SquashFS, which can be triggered by mounting a malicious or corrupted filesystem image. This vulnerability impacts the kernel's stability and security, potentially allowing an attacker with the ability to mount crafted SquashFS images to cause denial of service or possibly escalate privileges through memory corruption.

For European organizations, the impact of CVE-2023-52979 depends largely on their use of Linux systems that mount SquashFS filesystems. SquashFS is widely used in embedded devices, network appliances, container environments, and live Linux distributions, all common in enterprise and industrial settings. An attacker capable of providing a malicious SquashFS image—such as through removable media, network shares, or container images—could trigger kernel crashes leading to denial of service. In some scenarios, the out-of-bounds memory access could be leveraged for privilege escalation or arbitrary code execution, though no public exploits exist yet. This poses a risk to critical infrastructure, cloud providers, and organizations relying on Linux-based embedded systems or containerized workloads. Disruption of services due to kernel panics could impact availability of critical applications. Additionally, if exploited for privilege escalation, confidentiality and integrity of systems could be compromised. The threat is particularly relevant for sectors with high Linux adoption such as telecommunications, manufacturing, finance, and public administration across Europe. The lack of known exploits provides a window for proactive patching to mitigate risks before active exploitation occurs.

European organizations should prioritize updating their Linux kernels to versions that include the patch for CVE-2023-52979 as soon as vendor patches become available. Until patches are applied, organizations should restrict the mounting of untrusted or unauthenticated SquashFS images, especially from external or removable media sources. Implement strict validation and scanning of container images and filesystem images before deployment. Employ kernel hardening techniques such as Kernel Address Space Layout Randomization (KASLR), Kernel Page Table Isolation (KPTI), and seccomp filters to reduce exploitation risk. Monitor system logs for kernel oops or panic events related to SquashFS mounting operations to detect potential exploitation attempts. For embedded and IoT devices, coordinate with vendors to ensure timely firmware updates. Network segmentation and access controls can limit exposure to malicious filesystem images. Finally, incorporate this vulnerability into vulnerability management and incident response plans to ensure rapid detection and remediation.