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Fencer Intel
medium 6.5

CVE-2026-57565 json

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

published 27d ago modified 6d ago also EUVD-2026-117185 , GHSA-mfmj-2frf-vhgw

Unreviewed: the maintainers' own advisory

Published by the maintainers on their GitHub repository readest/readest. GitHub has not reviewed it into the GitHub Advisory Database, so the affected packages and versions are the maintainers' word. Read the full advisory on GitHub.

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.0%
EPSS 1.0% chance of exploitation in 30 days, percentile 64%
public exploits
0
none known

Summary

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.

Patch / fix

Is CVE-2026-57565 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
6d ago

Exploit prediction

1.04% chance of exploitation in the next 30 days, higher than 64% of all scored CVEs (FIRST EPSS, 2026-11-11).

Exploits and checks

  • github.com https://github.com/readest/readest/security/advisories/GHSA-mfmj-2frf-vhgw referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

Affected products

  • readest readest

Classification

Weakness
  • CWE-22 Improper Limitation of a Pathname to a Restricted Directory

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

The maintainers of readest/readest published their own advisory on GitHub. Reviewed sources take precedence over it.