---
id: CVE-2025-59028
title: >-
  When sending invalid base64 SASL data, login process is disconnected from the
  auth server, causing all active authentication sessions to fail
summary: >-
  When sending invalid base64 SASL data, login process is disconnected from the
  auth server, causing all active authentication sessions to fail. Invalid
  BASE64 data can be used to DoS a vulnerable server to break concurrent logins.
  Install…
severity: medium
cvss: 5.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'
cwe:
  - CWE-20
vendor: dovecot
product: dovecot
affected:
  - dovecot < 2.4.3
  - dovecot < 3.1.2
patched:
  - dovecot 3.1.2
published: '2026-03-27'
updated: '2026-09-30'
sourceUpdated: '2026-09-30T23:10:00.237'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-59028'
references:
  - url: >-
      https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0001.json
    label: security@open-xchange.com
tags:
  - nvd
epss: 0.00447
epssPercentile: 0.36475
ingestedAt: '2026-09-30T22:27:27.741Z'
---

## Overview

When sending invalid base64 SASL data, login process is disconnected from the auth server, causing all active authentication sessions to fail. Invalid BASE64 data can be used to DoS a vulnerable server to break concurrent logins. Install fixed version or disable concurrency in login processes (heavy perfomance penalty on large deployments). No publicly available exploits are known.

## Affected

- `dovecot < 2.4.3`
- `dovecot < 3.1.2`

## Remediation

Upgrade past the affected range:

- `dovecot 3.1.2`