# CVE-2026-93955: grimmory-tools grimmory Download Endpoint KoboController.java streamFileToResponse authorization

> Remote attackers can bypass authorization checks in the download endpoint to access unauthorized book files via manipulated bookId parameters.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 19 Sep 2026
- **Updated:** 21 Sep 2026
- **Also known as:** GHSA-frhf-rqp4-m3jc

## What is CVE-2026-93955?

CVE-2026-93955 is a medium-severity missing authorization vulnerability in grimmory-tools grimmory, published on 19 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

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.

Weakness: CWE-639 (Authorization Bypass Through User-Controlled Key), CWE-285 (Improper Authorization)

## Which versions are affected by CVE-2026-93955?


## How do I fix CVE-2026-93955?

No fix has been published for CVE-2026-93955 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-93955 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-93955 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93955 and fix it if it is affected.

What it is: CVE-2026-93955 is a medium-severity missing authorization vulnerability in grimmory-tools grimmory, published on 19 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-93955 exists.

Affected product: grimmory-tools grimmory. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-93955/ (Markdown: https://insights.sbomify.com/CVE-2026-93955/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93955
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93955
- OSV: https://osv.dev/vulnerability/CVE-2026-93955

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93955/
Summaries are generated and may contain mistakes; the official description above is the record.