---
id: CVE-2026-107585
title: >-
  Uncontrolled eviction in the pending sign-in tables of the REST API in
  Progressive Robot hMailServer 6.3.4 and 6.3.5 allows a remote unauthenticated
  attacker to make other users' OpenID Connect, SAML and passkey sign-ins fail
summary: >-
  Uncontrolled eviction in the pending sign-in tables of the REST API in
  Progressive Robot hMailServer 6.3.4 and 6.3.5 allows a remote unauthenticated
  attacker to make other users' OpenID Connect, SAML and passkey sign-ins fail.
  The routes…
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-770
vendor: Progressive Robot Ltd
product: hMailServer
affected:
  - hMailServer >= 6.3.4 < 6.3.6
published: '2026-10-08'
updated: '2026-10-08'
sourceUpdated: '2026-10-08T21:02:43.860'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-107585'
references:
  - url: 'https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6'
    label: cve@gitlab.com
  - url: 'https://gitlab.com/hmailserver/hmailserver/-/work_items/63'
    label: cve@gitlab.com
tags:
  - nvd
  - cve.org
ingestedAt: '2026-10-08T15:49:37.990Z'
---

## Overview

Uncontrolled eviction in the pending sign-in tables of the REST API in Progressive Robot hMailServer 6.3.4 and 6.3.5 allows a remote unauthenticated attacker to make other users' OpenID Connect, SAML and passkey sign-ins fail. The routes that start a single sign-on and hand out a passkey sign-in challenge are reached without authentication and stored pending state in bounded tables that dropped their oldest entry when full, whoever had started it. An attacker who starts sign-ins a few times a second (about a hundred a second for passkeys) pushes every other user's pending sign-in out of the table before that user's browser returns, denying single sign-on and passkey sign-in for as long as the requests continue.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.