CVE-2026-34041Public exploitNetwork attack vector

Workflow environment injection via deprecated command processing

Published Mar 31, 2026 · Updated Mar 31, 2026

Environment injection in Nektos act before 0.2.86 allows attackers to alter later workflow steps through crafted command output. The command handler in pkg/runner/command.go passes every ::set-env:: and ::add-path:: record from step stdout to setEnv or addPath without requiring the opt-in flag. Exploitation requires a workflow step to echo attacker-controlled text; injected variables or PATH entries then affect all later steps in that job.

CVSS severity7.7
High
EPSS probability0.62%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Environment injection in Nektos act before 0.2.86 allows attackers to alter later workflow steps through crafted command output. The command handler in pkg/runner/command.go passes every ::set-env:: and ::add-path:: record from step stdout to setEnv or addPath without requiring the opt-in flag. Exploitation requires a workflow step to echo attacker-controlled text; injected variables or PATH entries then affect all later steps in that job.

The record

CVE
CVE-2026-34041
Published
Mar 31, 2026
Updated
Mar 31, 2026
Vendor
Nektos
Product
act
Classifications
CWE-74, T1574.007
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 31, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 31, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 0.2.86

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Nektos · actversion=< 0.2.86

Published CVSS scores

7.7GitHub, Inc.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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
T1574.007Path Interception by PATH Environment Variable

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo