# arc has unauthenticated cluster node admission when \`cluster.shared_secret\` is unset

Advisory record · `GHSA-p378-jp5r-gpgw`

- **Identifiers:** `GHSA-p378-jp5r-gpgw` · `CVE-2026-55678` · `GO-2026-6322`
- **State:** Confirmed
- **Severity:** CVSS 6.9 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-284](https://cwe.mitre.org/data/definitions/284.html) · [CWE-287](https://cwe.mitre.org/data/definitions/287.html) · [CWE-306](https://cwe.mitre.org/data/definitions/306.html)
- **Tags:** [Broken access control](https://agentprime.io/advisories/tag/access-control.md) · [Authentication bypass](https://agentprime.io/advisories/tag/auth-bypass.md)
- **Published:** 28 Aug 2026
- **Updated:** 2 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 28 Aug 2026, 20:32 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `github.com/basekick-labs/arc` (Go): affected `<0.0.0-20260615160325-38402ad2ebdd`; fixed in `0.0.0-20260615160325-38402ad2ebdd`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> Arc Enterprise clustering in github.com/basekick-labs/arc accepts cluster join requests without authentication when cluster.enabled is true but cluster.shared_secret is not set; the affected version is before 0.0.0-20260615160325-38402ad2ebdd. A network attacker who can reach the coordinator port can join as a trusted node, receive forwarded requests that carry authentication headers, and alter cluster membership. Upgrade to 0.0.0-20260615160325-38402ad2ebdd, and set cluster.shared_secret when clustering is enabled.

Written 6 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 6.9 Medium, CVSS 4.0: `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0066, the 52nd percentile, on 14 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:47 UTC: First seen by agentprime
- 31 Oct 2026, 14:47 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-p378-jp5r-gpgw)

## Sources

- [GitHub Advisory Database: GHSA-p378-jp5r-gpgw](https://github.com/advisories/GHSA-p378-jp5r-gpgw)
- [OSV: GHSA-p378-jp5r-gpgw](https://osv.dev/vulnerability/GHSA-p378-jp5r-gpgw)
- <https://github.com/Basekick-Labs/arc/security/advisories/GHSA-p378-jp5r-gpgw>
- <https://github.com/Basekick-Labs/arc/pull/505>
- <https://github.com/Basekick-Labs/arc/commit/38402ad2ebddd32c15bf4a0fc9c22c920e5685df>
- <https://github.com/Basekick-Labs/arc>
- <https://github.com/Basekick-Labs/arc/releases/tag/v26.06.2>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-p378-jp5r-gpgw>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-p378-jp5r-gpgw/>. Everything for agents: <https://agentprime.io/llms.txt>.