CVE-2025-64750 is a vulnerability in Sylabs Singularity container platforms (SingularityCE and SingularityPRO) that allows an attacker to bypass Linux Security Module (LSM) restrictions by exploiting symbolic link following behavior. The issue arises when a user relies on LSM to prevent malicious operations within containers. An attacker can craft a malicious container image that remounts the /proc filesystem inside the container to a shared mount point. This shared mount must be either pre-configured on the target system or specified by the user at container runtime. The attacker must control the contents of this shared mount, which can be achieved by running another malicious container that binds the same mount or by having relevant permissions on the host system. By redirecting the LSM label write operation through this manipulated mount, the attacker effectively renders LSM restrictions ineffective, potentially allowing unauthorized operations within the container environment. The vulnerability affects SingularityCE versions greater than 4.2.0-rc.1 but less than 4.3.5, and SingularityPRO versions less than 4.1.11 and 4.3.5. The CVSS v3.1 base score is 4.5 (medium severity), reflecting local attack vector, high attack complexity, no privileges required, user interaction required, and limited impact on confidentiality, integrity, and availability. No known exploits have been reported in the wild. The issue was addressed in SingularityCE 4.3.5 and SingularityPRO 4.1.11 and 4.3.5.

For European organizations, especially those in scientific research, high-performance computing (HPC), and academic institutions that rely on Singularity containers for workload portability and security, this vulnerability poses a risk of bypassing LSM-based security controls. This could lead to unauthorized access or modification of containerized workloads, potentially exposing sensitive data or disrupting critical computations. Although the impact is limited by the requirement for local access and user interaction, the ability to circumvent security restrictions undermines trust in container isolation. This could facilitate lateral movement or privilege escalation within multi-tenant HPC clusters or shared research environments. The vulnerability may also affect organizations using Singularity in production environments for containerized applications, increasing the risk of data leakage or service disruption. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially in environments where attackers have insider access or where malicious container images could be introduced.

European organizations should immediately upgrade affected SingularityCE versions to 4.3.5 or later and SingularityPRO versions to 4.1.11 or later to obtain the official patch. Until upgrades are applied, restrict the use of shared mounts that can be manipulated by untrusted users or containers. Implement strict access controls on host systems to prevent unauthorized users from binding or modifying shared mounts. Enforce container image provenance and scanning policies to prevent running malicious container images. Limit user permissions to reduce the ability to specify arbitrary shared mounts at container runtime. Monitor container runtime logs and host filesystem mounts for suspicious remounting of /proc or unusual symlink activity. Consider additional runtime security tools that enforce mandatory access controls beyond LSM or provide container isolation verification. Educate users about the risks of running untrusted container images and the importance of following security best practices in containerized environments.