Bug 2453285 (CVE-2026-34041)

Summary: CVE-2026-34041 act: github.com/nektos/act: act: Privilege escalation and arbitrary code execution via environment variable injection
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: high    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in act, a project that allows local execution of GitHub Actions. This vulnerability arises from the unconditional processing of deprecated workflow commands, specifically ::set-env:: and ::add-path::, which were previously disabled due to environment injection risks. A remote attacker can exploit this by injecting these commands when a workflow step echoes untrusted data to standard output. This allows the attacker to set arbitrary environment variables or modify the system's execution path for all subsequent steps within the job, potentially leading to privilege escalation or arbitrary code execution.
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Bug Depends On: 2454355, 2454356, 2454357    
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Description OSIDB Bzimport 2026-03-31 03:02:35 UTC
act is a project which allows for local running of github actions. Prior to version 0.2.86, act unconditionally processes the deprecated ::set-env:: and ::add-path:: workflow commands, which was disabled due to environment injection risks. When a workflow step echoes untrusted data to stdout, an attacker can inject these commands to set arbitrary environment variables or modify the PATH for all subsequent steps in the job. This issue has been patched in version 0.2.86.