CVE-2026-34041
Nektos Act ≤ 0.2.86
Raw vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:XCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-34041 is a high-severity Injection (CWE-74) vulnerability in Nektos Act. Its CVSS base score is 7.7 (High).
Operationally, ranked in the top 46% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to SI-10 (Information Input Validation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-34041 is a high-severity vulnerability (CVSS 9.8, CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) affecting the 'act' project, a tool for running GitHub Actions workflows locally. In versions prior to 0.2.86, act unconditionally processes the deprecated ::set-env:: and ::add-path:: workflow commands, despite these being disabled in GitHub Actions due to environment injection risks (CWE-74). This flaw arises when a workflow step echoes untrusted data to stdout, enabling injection of these commands.
An attacker who can influence the input to a workflow step—such as through malicious repository content or untrusted actions—can exploit this remotely with low complexity and no privileges. Successful exploitation allows setting arbitrary environment variables or modifying the PATH for all subsequent steps in the job, potentially leading to command execution, data exfiltration, or full compromise of the local environment where act is running.
The issue was addressed in act version 0.2.86, as detailed in the project's security advisory (GHSA-xmgr-9pqc-h5vw), release notes, and patching commit. Security practitioners should upgrade to v0.2.86 or later and audit workflows for untrusted stdout outputs when using act locally.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-17287
Vulnerability Data
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…
more
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.
- CWE(s)
Related Threats
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
SI-10 directly requires validation of information inputs to reject malformed or special-element content before it reaches downstream parsers.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development catches injection vulnerabilities before release.
Monitoring activities can identify active injection attacks after they occur.
Secure coding standards require proper neutralization of special elements, directly addressing CWE-74.
Hardening callouts derived
DISA STIG baselines are authored against specific weaknesses. Where this CVE cites a broad weakness class, the mapping is not asserted at that abstraction (owner ruling, 2026-09-25: grade only at Base and below), so no rule is shown here rather than a rule shown against the wrong grain.
- No fine-grained STIG row for CWE-74, a class-level weakness, and none of its children carries one either.