CVE-2017-18641 in LXC
Summary
by MITRE
In LXC 2.0, many template scripts download code over cleartext HTTP, and omit a digital-signature check, before running it to bootstrap containers.
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Analysis
by VulDB Data Team • 04/22/2023
The vulnerability identified as CVE-2017-18641 affects LXC version 2.0 and represents a significant security weakness in container bootstrap processes. This flaw exists within the template scripts used to initialize containers, where the system downloads code using unencrypted http protocols instead of secure https connections. The absence of digital signature verification creates a critical attack surface that adversaries can exploit to compromise container environments. The vulnerability directly impacts the integrity and authenticity of code execution within containerized applications, potentially allowing malicious actors to inject compromised code during the container initialization phase.
The technical implementation of this vulnerability stems from the insecure handling of remote code downloads within LXC's template execution framework. When container templates are executed, they typically fetch necessary components from remote repositories to establish the container environment. In this case, the system defaults to cleartext http communications without implementing cryptographic verification mechanisms. This design flaw aligns with CWE-319, which addresses the exposure of sensitive information through cleartext transmission. The lack of digital signature verification means that any attacker who can intercept or manipulate network traffic between the container host and remote repositories can substitute legitimate code with malicious payloads.
The operational impact of this vulnerability extends beyond simple code execution, creating potential for complete container compromise and lateral movement within affected environments. Attackers can exploit this weakness through man-in-the-middle attacks or by compromising the network infrastructure to redirect traffic to malicious servers. Once compromised, the downloaded code executes with the privileges of the container initialization process, potentially escalating to system-level access depending on the container runtime configuration. This vulnerability particularly affects organizations relying on automated container deployment processes where template scripts are executed without manual intervention, making the attack surface more extensive and harder to detect. The risk is compounded in environments where containers are frequently updated or where automated deployment pipelines use LXC template systems.
Security mitigations for CVE-2017-18641 should prioritize immediate implementation of secure communication protocols and cryptographic verification mechanisms. Organizations must update to LXC versions that address this vulnerability by implementing https connections for all remote code downloads and enforcing digital signature validation before code execution. Network-level protections such as dns security extensions and secure proxy configurations can help mitigate traffic interception risks. The implementation of secure supply chain practices including code signing and integrity verification should be mandatory for all container template components. This vulnerability demonstrates the critical importance of secure coding practices and supply chain security, aligning with ATT&CK technique T1059.001 for command and scripting interpreter execution and T1566 for credential access through malicious code injection. Regular security assessments of container environments and network traffic monitoring should be implemented to detect potential exploitation attempts. Organizations should also consider implementing network segmentation and access controls to limit the potential impact of successful attacks, ensuring that compromised containers cannot be used as entry points for broader network infiltration.