CVE-2025-64750 is a vulnerability affecting Sylabs' Singularity container platforms, specifically 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 flaw arises from improper handling of symbolic link following in the context of Linux Security Module (LSM) label write operations. Under certain conditions, an attacker can cause the container runtime to redirect the mount point of /proc within a container to a shared mount point that the attacker controls. This redirection effectively bypasses LSM restrictions intended to prevent unauthorized operations, as the LSM label write operation is redirected and rendered ineffective. To exploit this vulnerability, the attacker must convince a user to run a malicious container image that performs this mount redirection. Additionally, the attacker must have control over the shared mount's contents, which could be achieved by running another malicious container that binds the shared mount or by having relevant permissions on the host system from which the shared mount originates. The vulnerability is categorized under CWE-61 (Improper Restriction of Symbolic Links) and CWE-706 (Use of Incorrectly-Resolved Name or Reference). The CVSS v3.1 base score is 4.5 (medium severity), reflecting that exploitation requires local access with high attack complexity, no privileges, and user interaction, and impacts confidentiality, integrity, and availability to a limited extent. No public exploits are known at this time. The issue is resolved in SingularityCE 4.3.5 and SingularityPRO 4.1.11 and 4.3.5.

For European organizations, especially those operating in research, scientific computing, and high-performance computing (HPC) environments where Singularity containers are widely used, this vulnerability could allow attackers to bypass security restrictions enforced by LSMs. This may lead to unauthorized access to sensitive data within containers, potential privilege escalation, or disruption of containerized workloads. Although the CVSS score is medium, the impact on confidentiality, integrity, and availability can be significant in environments processing sensitive or regulated data. The requirement for user interaction and local access limits remote exploitation but does not eliminate risk, particularly in multi-tenant HPC clusters or shared research infrastructures common in European academic and governmental institutions. Failure to patch could expose organizations to insider threats or lateral movement by attackers who have some level of access to the container environment.

European organizations should immediately upgrade affected SingularityCE and SingularityPRO deployments to versions 4.3.5 or later (for SingularityCE) and 4.1.11 or later (for SingularityPRO) to remediate this vulnerability. Additionally, administrators should audit and restrict permissions on shared mounts to prevent unauthorized control by untrusted containers or users. Implement strict container image provenance and scanning policies to prevent running malicious container images. Employ runtime monitoring to detect unusual mount operations or container behavior indicative of mount redirection attacks. Review and tighten LSM policies and consider additional container isolation mechanisms such as user namespaces or seccomp filters to reduce attack surface. Regularly review host system permissions to ensure that only trusted users have access to shared mounts used by containers. Finally, educate users about the risks of running untrusted container images and enforce policies to limit container image sources.