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CVE-2026-71209 – Unauthenticated Arbitrary File Read (Path Traversal / Auth-Exemption Bypass) – audi

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Summary

CVE-2026-71209 is a path traversal vulnerability (CWE-22) in advplyr’s audiobookshelf, a self-hosted audiobook and podcast server. A discrepancy between how the authentication-exemption check and Express’s route decoding handle URL-encoded input lets an unauthenticated attacker read arbitrary files on the server. It is rated High severity (CVSS 7.5).

Technical details

  • Root cause: The authentication-exemption check in server/routers/Auth.js matches unauthenticated-allowed GET routes against req.path using a regex that requires a literal /items/:id/cover or /authors/:id/image shape, where req.path still holds URL-encoded / sequences. Express’s router decodes the :id route parameter before handler code runs, so a percent-encoded ../ sequence in :id passes the literal-path exemption check while resolving to a real path-traversal payload once decoded.
  • Trigger conditions: An attacker sends a crafted request with percent-encoded traversal sequences (e.g. ..%2f..%2f..%2ftmp%2fpwned) to the cover/image endpoint. CacheManager.handleCoverCache (server/managers/CacheManager.js) then joins the decoded value into a cache file path and streams the result before any database-backed ownership check.
  • Attack vector: Network; no authentication and no user interaction required.
  • Impact: Unauthenticated arbitrary file read of any file matching the pattern *_<width>[x<height>].<ext> that the service account can read. This bypasses the fix applied for CVE-2025-25205.

Affected software

  • audiobookshelf versions 2.19.1 through 2.35.1

Severity

  • CVSS v3.1 base score: 7.5 (High)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Mitigation and recommended actions

  • Immediate: No fixed release is confirmed in the vendor advisory at time of writing. Monitor the advisory (GHSA-pg8v-5jcv-wrvw) and the project’s GitHub releases, and upgrade to the patched version as soon as it is published.
  • If no patch: Restrict network access to the audiobookshelf service so it is not reachable from untrusted networks; place it behind authenticated reverse-proxy or WAF rules that reject requests containing encoded traversal sequences; reduce the file-system permissions of the service account to limit readable files; and monitor request logs for path-traversal attempts.

How IONIX identifies potentially affected assets

IONIX matches the following signals against data already collected when it crawled the asset; identifying the technology sends no request beyond that crawl.

  • Page title: Audiobookshelf

References

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