# CVE-2026-40265: Note Mark has Broken Access Control on Asset Download

> Unauthenticated attackers can access private note assets by guessing IDs, exposing sensitive data in Note Mark applications.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Apr 2026
- **Updated:** 17 Apr 2026
- **Also known as:** GHSA-p5w6-75f9-cc2p, GO-2026-5530

## What is CVE-2026-40265?

CVE-2026-40265 is a medium-severity missing authorization vulnerability in enchant97 note-mark, published on 16 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Note Mark is an open-source note-taking application. In versions 0.19.1 and prior, the asset download endpoint at /api/notes/{noteID}/assets/{assetID} is registered without authentication middleware, and the backend query does not verify ownership or book visibility. An unauthenticated user who knows a valid note ID and asset ID can retrieve the full contents of private note assets without authentication, regardless of whether the associated book is public or private. This issue has been fixed in version 0.19.2.

Weakness: CWE-862 (Missing Authorization)

## Which versions are affected by CVE-2026-40265?

3 open source packages ship an affected version, including github.com/enchant97/note-mark/backend.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/enchant97/note-mark/backend` | Go | All versions | 0.0.0-20260411145023-6593898855ad |
| `github.com/enchant97/note-mark/backend` | Go | All versions | 0.0.0-20260411145023-6593898855ad |
| `github.com/enchant97/note-mark/backend` | Go | All versions | 0.0.0-20260411145023-6593898855ad |

## How do I fix CVE-2026-40265?

Upgrade github.com/enchant97/note-mark/backend to 0.0.0-20260411145023-6593898855ad or later.

## Is CVE-2026-40265 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40265 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40265 and fix it if it is affected.

What it is: CVE-2026-40265 is a medium-severity missing authorization vulnerability in enchant97 note-mark, published on 16 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40265 exists.

Affected packages and fixed versions:
- github.com/enchant97/note-mark/backend (Go): affected all versions; fixed in 0.0.0-20260411145023-6593898855ad
- github.com/enchant97/note-mark/backend (Go): affected all versions; fixed in 0.0.0-20260411145023-6593898855ad
- github.com/enchant97/note-mark/backend (Go): affected all versions; fixed in 0.0.0-20260411145023-6593898855ad

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-2026-40265/ (Markdown: https://insights.sbomify.com/CVE-2026-40265/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40265
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40265
- OSV: https://osv.dev/vulnerability/CVE-2026-40265

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-40265/
Summaries are generated and may contain mistakes; the official description above is the record.