CVE-2026-126613: Progressive Robot hMailServer · Unthrottled Resource Allocation
Affects Progressive Robot hMailServerSource CVE Database V5
Mentioned vulnerabilities
Not known to be exploited · CVSS 7.5 High · fixed in 6.3.6 : patch Progressive Robot hMailServer soon.
Data as of 11 Nov 2026, 08:49 UTC
Thin evidence
One scorer or none| CNA (GitLab) | CVSS 3.1 | 7.5 |
|---|
- Patch
- Available – fixed in 6.3.6
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 11 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 10 Nov 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Progressive Robot LtdhMailServer | Affected
| Fixed in– |
AI-suggested
No explicit patch or fix is stated in the provided data. If you cannot patch yet, administrators should consider disabling the REST API if not needed, restrict access to the REST API and webmail interfaces, and monitor for unusually large JSON payloads in TLS-RPT reports. Avoid enabling features that expose the JSON reader to unauthenticated remote attackers. Review mail server configurations to limit exposure to this attack vector.
Description
CVE-2026-126613 is a high-severity vulnerability in Progressive Robot Ltd's hMailServer versions 6.3.2 through 6.3.7. It involves allocation of resources without limits in the JSON reader, allowing remote attackers to exhaust server memory and threads. This causes unavailability of mail delivery, the REST API, and webmail services. The issue arises because the JSON reader builds a large tree of values without bounding the number of values, leading to excessive memory use from specially crafted JSON documents up to 16 MB in size. The vulnerability can be triggered via TLS-RPT reports, REST API requests, and webmail routes under certain configurations. This defect is distinct from CVE-2026-107574 and has no known exploits in the wild.