CVE-2026-103010 Heap-based Buffer Overflow in hMailServer
A local attacker can trigger a heap buffer overflow in hMailServer via an unauthenticated COM method, potentially achieving code execution as LocalSystem.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-103010?
CVE-2026-103010 is a high-severity memory corruption vulnerability in Progressive Robot Ltd hMailServer, published on 8 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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.
Weakness: CWE-122
Which versions are affected by CVE-2026-103010?
How do I fix CVE-2026-103010?
No fix has been published for CVE-2026-103010 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-103010 being exploited?
There is no known exploitation of CVE-2026-103010 in the wild and no public exploit code.
Sources
Also known as GHSA-mgwr-8mph-vj23.