Auth bypass in Grimmory-Tools Grimmory
CVE-2026-93955
A vulnerability was detected in grimmory-tools grimmory up to 3.3.3/3.4.1. Affected by this vulnerability is the function streamFileToResponse of the file backend/src/main/java/org/booklore/controller/KoboController.java of the component Download Endpoint. Performing a manipulation of the argument bookId results in authorization bypass. The attack may be initiated remotely. The exploit is now public and may be used. Issue #2431 is closed as completed, but its only comment states that the issue “has already been reported elsewhere.” No fixing commit or pull request is identified there.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N.
EPSS exploit prediction
EPSS: 0.004 (35.7th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 36th percentile — 35.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000
Affected products
- Grimmory-Tools Grimmory — versions 3.3.0, 3.3.1, 3.3.2
Weakness classification (CWE)
References
- vuldb.com/vuln/407914 (technical-description, vdb-entry)
- vuldb.com/vuln/407914/cti (signature, permissions-required)
- vuldb.com/cve/CVE-2026-93955 (third-party-advisory)
- vuldb.com/submit/943921 (third-party-advisory)
- github.com/grimmory-tools/grimmory/issues/2431 (issue-tracking, exploit)
- github.com/grimmory-tools/grimmory/issues/2431 (issue-tracking)
- github.com/grimmory-tools/grimmory/ (product)
Frequently asked questions
- What is CVE-2026-93955?
- CVE-2026-93955 is a medium-severity vulnerability in Grimmory-Tools Grimmory, classified under Improper Authorization. CVSS score: 4.3/10. Published 2026-09-19.
- How severe is CVE-2026-93955?
- Medium severity. CVSS v3 base score is 4.3 out of 10.