# CVE-2026-40020: Attacker can use the IMAP SETACL command to inject the anyone permission to user's dovecot-acl file even if imap_acl_allow_anyone=no.


- **Severity:** Low 3.1 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 12 May 2026
- **Updated:** 12 May 2026
- **Also known as:** ALPINE-CVE-2026-40020, AZL-86808, DEBIAN-CVE-2026-40020, GHSA-h6rp-9mjf-6x88, UBUNTU-CVE-2026-40020

## What is CVE-2026-40020?

CVE-2026-40020 is a low-severity vulnerability in Dovecot Dovecot, published on 12 May 2026. 

### Official description

Attacker can use the IMAP SETACL command to inject the anyone permission to user's dovecot-acl file even if imap_acl_allow_anyone=no. This causes folders to be spammed to all users. The impact is limited to being able to spam folders to other users, no unexpected access is gained. Install to fixed version. No publicly available exploits are known.

Weakness: CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2026-40020?

It affects 2 products.


Products: Dovecot Dovecot, Open-Xchange Dovecot.

## How do I fix CVE-2026-40020?

Upgrade to a fixed version.

## Is CVE-2026-40020 being exploited?

There is no known exploitation of CVE-2026-40020 in the wild and no public exploit code.

## Other vulnerabilities in Dovecot Dovecot

- [CVE-2026-24031](https://insights.sbomify.com/CVE-2026-24031/): Auth bypass in OX Dovecot Pro (high 7.7)
- [CVE-2025-59032](https://insights.sbomify.com/CVE-2025-59032/): Denial of service in OX Dovecot Pro (high 7.5)
- [CVE-2026-27858](https://insights.sbomify.com/CVE-2026-27858/): Denial of service in OX Dovecot Pro (high 7.5)
- [CVE-2021-29157](https://insights.sbomify.com/CVE-2021-29157/): Path traversal in n/a (high 7.5)
- [CVE-2020-10957](https://insights.sbomify.com/CVE-2020-10957/): Null dereference in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40020 and fix it if it is affected.

What it is: CVE-2026-40020 is a low-severity vulnerability in Dovecot Dovecot, published on 12 May 2026. 
Exploitation: There is no known exploitation of CVE-2026-40020 in the wild and no public exploit code.

Affected product: Dovecot Dovecot. 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-2026-40020/ (Markdown: https://insights.sbomify.com/CVE-2026-40020/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40020
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40020
- OSV: https://osv.dev/vulnerability/CVE-2026-40020

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-40020/
Summaries are generated and may contain mistakes; the official description above is the record.