Improper Certificate Validation in hMailServer
Summary
| CVE | CVE-2026-107587 |
|---|---|
| State | PUBLISHED |
| Assigner | GitLab |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-10-08 12:17:16 UTC |
| Updated | 2026-10-08 12:17:16 UTC |
| Description | Improper certificate validation in the webmail of Progressive Robot hMailServer 6.3.2 through 6.3.5 allows a remote unauthenticated attacker to have S/MIME-encrypted mail that the account later sends to another correspondent also encrypted to the attacker's key. When its recipient opened a signed message, the webmail kept the signer's certificate for encrypting replies whether or not the server found its chain trusted, under the first e-mail address the certificate listed rather than the message's From address, and beside any certificate already held for that address. Encrypted mail later sent from the webmail to that address was encrypted to every certificate held for it, so a holder of the kept certificate's key who obtains a copy of such a message can read it. |
Risk And Classification
Primary CVSS: v3.1 5.9 MEDIUM from [email protected]
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:L/A:N
Problem Types: CWE-295 | CWE-295 CWE-295: Improper Certificate Validation
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Secondary | 5.9 | MEDIUM | CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:L/A:N |
| 3.1 | CNA | CVSS | 5.9 | MEDIUM | CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:L/A:N |
CVSS v3.1 Breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:L/A:N
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Progressive Robot Ltd | HMailServer | affected 6.3.2 6.3.6 semver | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| gitlab.com/hmailserver/hmailserver/-/work_items/66 | [email protected] | gitlab.com | |
| gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6 | [email protected] | gitlab.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Found in the hMailServer project's own security review (Progressive Robot Ltd) (en)
Additional Advisory Data
Solutions
CNA: Upgrade to hMailServer 6.3.6, whose webmail keeps a signer's certificate only when its chain is trusted, only under the From address the signature was verified for, and a different certificate for an address that has one only when the reader chooses to. After upgrading, review the correspondents' certificates on the webmail's Security page and remove any that should not be there. Until then: check the certificates listed for an address before sending it encrypted mail from the webmail, or encrypt in a mail program.