CVE-2026-53970 in ZeroBrew
Summary
by MITRE • 08/14/2026
ZeroBrew version 0.3.1 and prior contains a missing integrity verification vulnerability in the Ruby compatibility shim that allows network attackers to execute arbitrary code by substituting malicious content at formula resource or URL-based patch URLs without checksum validation. Attackers can intercept or replace downloads for secondary resource and patch paths in shim.rb, injecting attacker-controlled build steps or source tree modifications that execute during source builds via 'zb install --build-from-source' without any integrity warning.
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Analysis
by VulDB Data Team • 08/14/2026
The ZeroBrew Ruby compatibility shim vulnerability represents a critical security flaw that undermines the integrity of software package installations through its handling of external resource dependencies. This vulnerability affects versions 0.3.1 and earlier, where the shim fails to implement proper checksum validation mechanisms when processing formula resources or URL-based patch files. The absence of integrity verification creates an attack surface that allows remote adversaries to manipulate the build process by substituting legitimate resources with malicious content without detection. The vulnerability specifically targets the shim.rb component which serves as a bridge between ZeroBrew's package management system and Ruby-based dependencies, making it a crucial point of failure in the software supply chain.
The technical implementation of this flaw stems from the lack of cryptographic verification checks within the resource download and processing pipeline. When ZeroBrew executes 'zb install --build-from-source' commands, the shim component retrieves external resources through HTTP or HTTPS connections without validating their integrity against expected checksums or digital signatures. This absence of verification allows attackers to perform man-in-the-middle attacks by intercepting network traffic and replacing legitimate files with malicious counterparts. The vulnerability operates at the level of secondary resource handling where patch files and additional dependencies are downloaded during the build process, creating a window of opportunity for code injection attacks that can execute arbitrary commands during compilation.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass full system compromise through supply chain attacks. Attackers can exploit this weakness to inject malicious code into the build environment by replacing legitimate patches or resource files with attacker-controlled content. The injected code executes during the source compilation phase, potentially leading to persistent backdoors, data exfiltration capabilities, or further system exploitation. This vulnerability particularly affects environments where ZeroBrew is used for package management and software deployment, as it undermines the trust model that users expect from package managers and build systems. The lack of integrity warnings during installation means that administrators remain unaware of compromised resources until potentially malicious behavior manifests.
Security mitigations for this vulnerability should focus on implementing robust checksum validation mechanisms throughout the resource handling pipeline. Organizations should immediately upgrade to patched versions of ZeroBrew where proper cryptographic verification has been implemented for all external resource downloads. The remediation process must include mandatory verification of SHA-256 or similar cryptographic hashes for all formula resources and patch files before installation. Additionally, network administrators should implement traffic inspection mechanisms to detect suspicious modifications to download streams and establish secure communication channels with certificate pinning where applicable. This vulnerability aligns with CWE-347, which addresses improper validation of cryptographic signatures, and maps to ATT&CK technique T1583.002 for supply chain compromise through malicious code injection in build dependencies. The implementation of these security controls should follow industry standards such as NIST SP 800-53 for secure software development practices and ensure proper defense-in-depth measures are maintained throughout the software lifecycle.