CVE-2020-29529 in go-slug
Summary
by MITRE • 12/04/2020
HashiCorp go-slug up to 0.4.3 did not fully protect against Zip Slip attacks while unpacking tar archives, and protections could be bypassed with specific constructions of multiple symlinks. Fixed in 0.5.0.
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Analysis
by VulDB Data Team • 08/31/2025
The vulnerability identified as CVE-2020-29529 affects HashiCorp's go-slug library version 0.4.3 and earlier, representing a critical security flaw in archive extraction handling that exposes systems to Zip Slip attack vectors. This issue specifically manifests during the unpacking of tar archives where the library fails to provide complete protection against directory traversal attacks that could allow malicious actors to write files outside of intended directories. The vulnerability stems from inadequate validation mechanisms within the archive extraction process, particularly when dealing with symbolic link constructions that can bypass existing safeguards.
The technical implementation flaw resides in how go-slug processes tar archive entries during decompression, where it does not sufficiently validate file paths or handle symbolic links in a manner that prevents arbitrary file system access. Attackers can exploit this by crafting malicious tar archives containing carefully constructed symbolic links that, when processed by the vulnerable library, can cause files to be written to unintended locations on the target system. This bypass mechanism specifically targets the library's symlink handling capabilities, allowing attackers to circumvent the intended directory restrictions that should contain file extraction operations within designated boundaries.
The operational impact of this vulnerability extends beyond simple directory traversal, as it can enable attackers to overwrite critical system files, inject malicious code into existing processes, or establish persistent access points within the target environment. When exploited in automated systems or continuous integration pipelines that utilize go-slug for artifact extraction, the consequences can be severe and far-reaching. The vulnerability particularly affects environments where tar archives are processed without proper sandboxing or privilege separation, creating opportunities for privilege escalation and system compromise. Organizations relying on HashiCorp tools for infrastructure automation and deployment processes face significant risk if they have not updated to version 0.5.0 or later, as the attack surface includes any system that processes untrusted tar archives through this library.
Mitigation strategies for CVE-2020-29529 require immediate deployment of go-slug version 0.5.0 or later, which includes enhanced protections against Zip Slip attacks through improved path validation and symlink handling. Security teams should conduct comprehensive audits of systems that utilize go-slug or any HashiCorp tools that may be vulnerable to similar path traversal issues, implementing additional safeguards such as process isolation, privilege reduction, and input validation layers. The fix addresses the core issue by strengthening the validation of archive entry paths and ensuring that symbolic link resolution does not bypass directory containment policies. Organizations should also consider implementing network-based protections such as firewalls and intrusion detection systems to monitor for suspicious archive extraction activities, while following industry best practices outlined in CWE-22 for path traversal vulnerabilities and ATT&CK technique T1059.007 for execution through archive extraction. Regular security assessments and dependency updates should be integrated into organizational security practices to prevent similar vulnerabilities from emerging in other components of the software supply chain.