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CVE.org (no NVD analysis yet)· CNA GitLab

CVE-2026-126610: Improper Certificate Validation in hMailServer

HighCVSS 7.4 · v3.1—No exploit No fix recorded

Noroxi assessment

Priority: Monitor (action score 29/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.16% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
  • According to the record, no fixed version is available yet.

Low priority for now. Update when a fix is released; follow the vendor's advisory.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

Published
Nov 11, 2026
Updated
Nov 12, 2026
EPSS
0.1% · 6th percentile

Report tools

JSON

Action score

29

Monitor

Low priority for now.

CVSS
29 / 40 · 7.4 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CNA vs NVD score

NVD
—
CNA · GitLab
7.4
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • No fixed version yet

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When you'll hear from us

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  • when exploit code appears or is weaponized
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  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

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This vulnerability is about certificate validation or weak cryptography. The free SSL checker tests your certificate, enabled TLS versions and weak ciphers.

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Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitLab). Independent of NVD's CPE analysis and usually ahead of it.

  • Progressive Robot Ltd hMailServer

    • 6.3.4 and later · up to and including 6.3.7affected · semver

Same product

progressive robot ltd: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-100741Improper Neutralization of Directives in Dynamically Evaluated Code ('Eval Injection') in hMailServer
    40Plan
  • CVE-2026-126617Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection') in hMailServer
    35Monitor
  • CVE-2026-114489Missing Authorization in hMailServer
    32Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2026-126607Nov 11, 2026 · Uncontrolled Search Path Element in hMailServer
    31Monitor
  • ← EarlierCVE-2026-126609Nov 11, 2026 · Improper Certificate Validation in hMailServer
    30Monitor
  • Later →CVE-2026-126611Nov 11, 2026 · Improper Certificate Validation in hMailServer
    28Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-1266090 days apartImproper Certificate Validation in hMailServer
    30Monitor
  • CVE-2026-1266210 days apartImproper Certificate Validation in hMailServer
    30Monitor
  • CVE-2026-1266110 days apartImproper Certificate Validation in hMailServer
    28Monitor
  • CVE-2026-10758734 days apartImproper Certificate Validation in hMailServer
    23Monitor

Not on record for this CVE: patch commit or PR link · public bounty program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
none
Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
None

Weakness class (CWE)

CWE-295 · Improper Certificate Validation

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

nvd-secondary

Root cause

A certificate validation error is silently swallowed instead of terminating the connection. Often, code added for a test environment makes its way into production.

The bug in code

The whole CWE-295 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

kotlin
override fun checkServerTrusted(chain: Array<X509Certificate>, type: String) {  // Left empty for the test environment}

Fixed

kotlin
val client = OkHttpClient.Builder()  .certificatePinner(    CertificatePinner.Builder()      .add("api.sirius.example", "sha256/…")      .build()  ).build()

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

References

Show all references (1 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

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