CVE-2025-37780 is a vulnerability identified in the Linux kernel's ISO 9660 filesystem implementation, specifically within the isofs module. The flaw arises from an out-of-bounds read condition in the function isofs_fh_to_parent, which is responsible for converting file handles to parent directory references. The vulnerability occurs because the code allocates only 12 bytes for the file_handle->f_handle member, but subsequently accesses the parent_block member of the isofs_fid structure, which requires at least 16 bytes. This mismatch leads to a slab-out-of-bounds read, as confirmed by Kernel Address Sanitizer (KASAN) reports. The issue was detected by syzbot, an automated kernel fuzzer, which triggered the bug by passing a handle_bytes value of 12, insufficient for safe access to parent_block. The kernel call stack shows the fault occurs during the processing of open_by_handle_at system calls, which are used to open files via file handles rather than traditional pathnames. Although no known exploits are currently reported in the wild, the vulnerability could potentially be triggered by a local attacker or malicious process with the ability to invoke these system calls. The problem affects specific Linux kernel versions identified by the commit hash 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and was publicly disclosed in May 2025. The root cause is a logic error in memory allocation size and boundary checking within the isofs filesystem code, leading to an out-of-bounds memory read that could cause kernel crashes or information leakage. The vulnerability does not require user interaction but does require the ability to execute system calls that interact with the isofs filesystem, which is commonly used for ISO images and CD-ROM filesystems.

For European organizations, the impact of CVE-2025-37780 depends on the deployment of Linux systems utilizing the isofs filesystem, particularly those that mount ISO images or use CD-ROM filesystems. While the vulnerability is a read out-of-bounds error, it can lead to kernel crashes (denial of service) or potentially expose kernel memory contents, which may include sensitive information. This could disrupt critical services running on Linux servers, especially in sectors like finance, healthcare, and government where Linux is prevalent. Additionally, organizations using containerized environments or virtual machines on Linux hosts might face stability issues if the underlying kernel is vulnerable. Although exploitation requires local access and the ability to invoke specific system calls, insider threats or compromised accounts could leverage this flaw to escalate impact. The absence of known exploits reduces immediate risk, but the vulnerability's presence in widely used Linux kernels necessitates prompt attention. The impact on confidentiality, integrity, and availability is primarily availability (due to possible crashes) and confidentiality (due to potential memory disclosure).

To mitigate CVE-2025-37780, European organizations should: 1) Apply the latest Linux kernel patches that address this vulnerability as soon as they become available, ensuring that the isofs module correctly allocates sufficient memory and performs proper boundary checks. 2) Audit systems to identify usage of the isofs filesystem and limit mounting of untrusted ISO images or CD-ROM filesystems, reducing attack surface. 3) Restrict local user privileges to prevent unauthorized invocation of open_by_handle_at system calls on isofs mounts. 4) Employ kernel hardening techniques such as Kernel Address Sanitizer (KASAN) in testing environments to detect similar issues proactively. 5) Monitor system logs for unusual kernel warnings or crashes related to isofs operations, enabling early detection of exploitation attempts. 6) Where feasible, disable or remove support for isofs if not required, minimizing exposure. 7) Incorporate this vulnerability into vulnerability management and incident response plans to ensure rapid remediation and response.