CVE-2026-107585: CWE-770: Allocation of Resources Without Limits or Throttling in Progressive Robot Ltd hMailServer
Description
CVE-2026-107585 is a medium severity vulnerability in Progressive Robot Ltd's hMailServer versions 6.3.4 and 6.3.5. It involves uncontrolled eviction in the REST API's pending sign-in tables used for OpenID Connect, SAML, and passkey single sign-on. An unauthenticated remote attacker can repeatedly start sign-ins to evict other users' pending sign-in states, causing denial of service for single sign-on and passkey sign-in until the attack stops.
CVSS v3.1
Score 5.3medium
Affected software
Progressive Robot Ltd
hMailServer
pkg:github/hmailserver/hmailserverRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability arises from bounded pending sign-in tables in the REST API of hMailServer 6.3.4 and 6.3.5 that drop the oldest entry when full. These tables store state for unauthenticated routes initiating single sign-on and passkey sign-in challenges. An attacker can flood these routes with sign-in requests at a rate of about 100 per second for passkeys, pushing out legitimate users' pending sign-in entries before their browsers complete the process. This results in denial of service for other users' OpenID Connect, SAML, and passkey sign-ins. The issue is classified under CWE-770 (Allocation of Resources Without Limits or Throttling).
Potential Impact
The impact is denial of service on single sign-on and passkey sign-in functionality for legitimate users. There is no confidentiality or integrity impact reported. The vulnerability allows remote unauthenticated attackers to disrupt authentication flows by exhausting the pending sign-in table capacity.
Mitigation Recommendations
No official patch or fix is indicated in the provided data. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, consider implementing rate limiting or other throttling mechanisms on the affected REST API endpoints to reduce the risk of resource exhaustion attacks.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitLab
- Date Reserved
- 2026-10-08T10:52:30.638Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6ac7b46a2cdf04f656230dc8
Added to database: 10/08/2026, 15:19:06 UTC
Last enriched: 10/08/2026, 15:33:37 UTC
Last updated: 10/08/2026, 15:36:12 UTC
Views: 5
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