TI-2026-69488 Aliases CVE-2026-103010

Heap buffer overflow in hMailServer Blowfish decryption routine

LOW 35CWE-122Published 2026-10-08 · Updated 2026-10-08

Key facts

Attack vector: Local
Privileges required: Low
User interaction: None
Attack complexity: Low
Impact type: Code execution
Confidentiality · integrity · availability: High · High · High
Fix status: Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-122 and the CVSS impact.

Summary

Progressive Robot hMailServer from 6.0.0 before 6.3.4 on Windows contains a heap-based buffer overflow (CWE-122) in its legacy Blowfish decryption routine. The routine copies hexadecimal input of any length into a fixed 255-byte buffer, so a local interactive user with no hMailServer credentials can write past the end of that buffer. The result is a denial of service through a service crash, and possibly code execution with the privileges of the service account.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

Description from the CNA

Heap-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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00162 5th percentileScored 2026-11-07

Fix Fixed hMailServer (Progressive Robot Ltd): 6.3.4

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
Progressive Robot Ltd	hMailServer	6.0.0 to before 6.3.4	6.3.4	Patch available	CNA

hMailServer VendorProgressive Robot Ltd Affected 6.0.0 to before 6.3.4 Fixed in 6.3.4 Patch available CNA

Remediation

Upgrade Progressive Robot hMailServer to version 6.3.4, the fixed version.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

Fix · CNA hMailServer (Progressive Robot Ltd) Fixed in 6.3.4

Timeline

2026-10-08 Threatist record created from CVE-2026-103010

References

Other 3

TI-2026-64884 Improper Neutralization of Directives in Dynamically Evaluated Code ('Eval Injection') in hMailServer CVSS 3.1CRITICAL 9.8
TI-2026-76418 Unchecked loop limit in hMailServer lets remote attackers stop mail CVSS 3.1HIGH 7.5
TI-2026-69567 Inefficient processing in hMailServer stalls mail delivery CVSS 3.1HIGH 7.5
TI-2026-69565 Infinite loop in hMailServer MIME handling lets attackers stop mail CVSS 3.1HIGH 7.5
TI-2026-69564 Inefficient DKIM and ARC checks in hMailServer cause denial of service CVSS 3.1HIGH 7.5
TI-2026-69562 Inefficient JSON parsing in hMailServer lets attackers halt mail CVSS 3.1HIGH 7.5

See all 41 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences