Insufficient resource pool in the ACME HTTP-01 challenge responder of Progressive Robot hMailServer 6.0.0 through 6.3.6 allows a remote unauthenticated attacker to cause a certificate issuance or renewal to fail. When the server obtains or renews a TLS certificate over ACME it runs an HTTP-01 challenge responder on port 80 for the certificate authority to read the challenge token; the responder served one connection at a time, accepting a socket, waiting up to five seconds to receive a request, answering it, and only then accepting the next. A client that connected and sent nothing held the single worker for the whole timeout, so enough idle connections during a validation keep the certificate authority's own request from being answered in time and the validation fails. Sustained across a certificate's renewals this leads to the certificate expiring, after which clients refuse the server's TLS; the mail service itself continues on its current certificate until then. No authentication is required to connect to the responder. Version 6.3.7 serves up to 64 connections at once and closes a connection past that, so that where a handful of idle connections, one after another, sufficed before, a client must keep 64 idle connections open at once throughout a validation to have the certificate authority's connection closed.
References
Configurations
No configuration.
History
21 Oct 2026, 16:17
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2026-10-21 16:17
Updated : 2026-10-29 21:17
NVD link : CVE-2026-114472
Mitre link : CVE-2026-114472
CVE.ORG link : CVE-2026-114472
JSON object : View
Products Affected
No product.
CWE
CWE-410
Insufficient Resource Pool