Heap-based Buffer Overflow in hMailServer

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-103010
StatePUBLISHED
AssignerGitLab
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-08 11:16:42 UTC
Updated2026-10-08 21:02:43 UTC
DescriptionHeap-based buffer overflow in the legacy Blowfish decryption routine (BlowFishEncryptor::DecryptFromString) in Progressive Robot hMailServer 6.0.0 through 6.3.3 on Windows allows a local interactive user with no hMailServer credentials to write bytes of their choosing past the end of a 255-byte heap buffer in the hMailServer service process, which runs as LocalSystem by default. The user does this by passing a long hexadecimal string to the COM method Utilities.BlowfishDecrypt, which checked no authentication. The routine converted hexadecimal input of any length into a fixed 255-byte buffer before decrypting it in place. The result is a denial of service (service crash), and possibly code execution with the privileges of the service account.

Risk And Classification

Primary CVSS: v3.1 7.8 HIGH from [email protected]

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

EPSS: 0.001620000 probability, percentile 0.049150000 (date 2026-10-10)

Problem Types: CWE-122 | CWE-122 CWE-122: Heap-based Buffer Overflow

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1CNACVSS7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Progressive Robot Ltd HMailServer affected 6.0.0 6.3.4 semver Not specified

References

ReferenceSourceLinkTags
gitlab.com/hmailserver/hmailserver/-/work_items/49 [email protected] gitlab.com
gitlab.com/hmailserver/hmailserver/-/releases/v6.3.4 [email protected] gitlab.com
gitlab.com/hmailserver/hmailserver/-/commit/135a1908ff820ed587d5f180f98c... [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 code review (Progressive Robot Ltd) (en)

Additional Advisory Data

Solutions

CNA: Upgrade to hMailServer 6.3.6, which also requires authentication for the COM Utilities helpers (6.3.4 is the first release with this routine fixed).

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