Improper Certificate Validation in hMailServer
Summary
| CVE | CVE-2026-126610 |
|---|---|
| State | PUBLISHED |
| Assigner | GitLab |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-11-11 09:17:12 UTC |
| Updated | 2026-11-11 09:17:12 UTC |
| Description | Progressive Robot hMailServer 6.3.4 through 6.3.7, with a MySQL or MariaDB database and TlsMode=verify-full, does not hand the database client the CA file that TlsCaFile names when the file's name contains a character outside ASCII on Linux, or above U+00FF on Windows, which allows an attacker who can intercept the connection to the database server to read and modify the traffic between hMailServer and its database, by presenting, with MariaDB Connector/C 3.4.2 to 3.4.10 as the client, a certificate from any authority, its own included, for any name, and otherwise a certificate for the database server's name issued by any certificate authority in the system's trust store. The server converted the name for the client with the C runtime's conversion in the C locale, which gives an empty string for such a name, and then set no CA file at all, without an error, while certificate verification stayed on, so the client - MariaDB Connector/C, bundled on Windows and the distribution's on Linux - verified the certificate of a database server over the network against the system's trust store instead of the configured CA; Connector/C 3.4.2 to 3.4.10 (bundled on Windows in 6.3.4 to 6.3.6) went further and, with no CA file, took a certificate within its dates whose issuer it could not find, for any name, with neither its chain nor its name checked and no password proof, when the server offered first a sign-in method that hashes the password, which an attacker in the middle chooses (MariaDB's CONC-853, fixed in Connector/C 3.4.11), and Connector/C 3.4 accepted from a MariaDB 11.4 or later server a certificate the store did not vouch for when that server proved it held the account's password; on a connection it treats as local (127.0.0.1, ::1, a Unix socket, a named pipe, and localhost on Windows), Connector/C 3.4.1 and later checked neither the certificate's issuer nor its name, so that a local attacker able to stand in for the database server could present any certificate within its dates of its own making. The settings line of hmailserver --check-database still named the configured file, and the application log said the certificate had been checked. With MariaDB Connector/C 3.4.1 to 3.4.9 as the client - bundled on Windows in 6.3.4 to 6.3.6, and the client of Linux distributions that have not patched it - the missing CA file also met the precondition of CVE-2026-107819, so that a certificate issued for any other name by a trusted authority was enough to obtain the database password. On Linux the file was found only when the server ran on glibc under a locale whose character set holds the name's characters (a UTF-8 locale, or a legacy 8-bit one the system has, in whose bytes the file is then named); with no locale, LC_ALL=C or a locale the system lacks, and on Alpine (musl), the connection failed instead. The configuration is not the default: TlsMode defaults to prefer, which checks no certificate. |
Risk And Classification
Primary CVSS: v3.1 7.4 HIGH from [email protected]
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Problem Types: CWE-295 | CWE-295 CWE-295: Improper Certificate Validation
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Secondary | 7.4 | HIGH | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N |
| 3.1 | CNA | CVSS | 7.4 | HIGH | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N |
CVSS v3.1 Breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Progressive Robot Ltd | HMailServer | affected 6.3.4 6.3.7 semver | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| gitlab.com/hmailserver/hmailserver/-/work_items/112 | [email protected] | gitlab.com | |
| gitlab.com/hmailserver/hmailserver/-/releases/v6.3.8 | [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 by the hMailServer project (Progressive Robot Ltd) (en)
Additional Advisory Data
Solutions
CNA: Upgrade to hMailServer 6.3.8, which hands the database client the CA file's name in the encoding the client opens it in - UTF-8 on Linux whatever the locale, the ANSI code page on Windows - and refuses before connecting, with HM7534 in the error log, a name it cannot write so, never handing over an empty one. Until then, give TlsCaFile a path in ASCII alone, which every affected version hands to the client as it is; on these versions the settings line of hmailserver --check-database names the configured file whether or not the client was given it, so it does not show the difference. On Linux, also update the distribution's MariaDB Connector/C to 3.4.11 or later, which fixes both CVE-2026-107819 and CONC-853, where one is offered; a version with the fix for CVE-2026-107819 alone still accepts a certificate whose issuer it cannot find.