CVE-2020-13847 in Singularity
Summary
by MITRE • 01/25/2023
Sylabs Singularity 3.0 through 3.5 lacks support for an Integrity Check. Singularity's sign and verify commands do not sign metadata found in the global header or data object descriptors of a SIF file.
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Analysis
by VulDB Data Team • 01/25/2023
The vulnerability identified as CVE-2020-13847 affects Sylabs Singularity container runtime versions 3.0 through 3.5, specifically addressing a critical weakness in the software's integrity verification mechanisms. This flaw resides in the absence of proper integrity checking capabilities within the container image signing and verification processes, creating a significant security gap that undermines the trustworthiness of containerized applications. The issue impacts the SIF file format which serves as the container image format for Singularity, where the global header and data object descriptors contain metadata essential for verifying the authenticity and integrity of container images.
The technical flaw manifests in the sign and verify commands of Singularity's toolset, which fail to implement comprehensive signature validation for all metadata components within SIF files. This limitation means that while users can sign container images, the signatures only cover certain portions of the image data while leaving critical structural elements unprotected. The global header and data object descriptors, which contain essential information about the container's structure, content, and metadata, remain unsigned and therefore vulnerable to tampering without detection. This architectural oversight creates a scenario where malicious actors could modify container images at the structural level without breaking the signature verification process, effectively bypassing the intended security controls.
From an operational impact perspective, this vulnerability significantly weakens the security posture of organizations relying on Singularity container environments for scientific computing and research workloads. The lack of integrity checking for critical metadata elements means that even signed container images may contain modified structural components that could execute malicious code or alter the intended behavior of applications. This weakness particularly affects environments where container images are shared across organizations or downloaded from untrusted sources, as it allows for undetected modifications to the container's internal structure that could compromise system integrity. The vulnerability essentially undermines the principle of defense in depth, as the signing mechanism becomes ineffective for protecting against certain types of attacks targeting container image integrity.
The flaw aligns with CWE-347, which addresses improper certificate validation and weak cryptographic integrity checks, and relates to ATT&CK technique T1553.004 for Valid Code Signing, where the absence of comprehensive integrity checking allows for potential code injection attacks. Organizations using Singularity versions within the affected range should immediately implement mitigation strategies including updating to patched versions, implementing additional verification layers, and establishing more rigorous image sourcing controls. The recommended approach involves upgrading to Singularity 3.5.1 or later, where comprehensive integrity checking has been implemented, along with implementing continuous monitoring of container image integrity and establishing secure image distribution practices that include multiple verification mechanisms beyond the single signature approach.