EUVD-2026-94837
GHSA-mgwr-8mph-vj23
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Local COM access needs a logon session (AV:L, PR:L) with no user interaction or app auth, and an overflow in a LocalSystem service gives full C/I/A.
Primary rating from Vendor (GitLab).
CVSS VectorVendor: GitLab
Lifecycle Timeline
4DescriptionCVE.org
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.
AnalysisAI
Heap-based buffer overflow in hMailServer 6.0.0 through 6.3.3 on Windows lets a local interactive user - with no hMailServer account - crash the mail server service and potentially execute code in its LocalSystem security context by passing an over-long hexadecimal string to the unauthenticated COM method Utilities.BlowfishDecrypt, which copies input of arbitrary length into a fixed 255-byte heap buffer. Because exploitation requires an existing local login (CVSS AV:L/PR:L) and the only confirmed outcome is a service crash, this is an access-gated local privilege-escalation/denial-of-service issue rather than a remotely wormable emergency; no public exploit identified at time of analysis. …
Unlock full vulnerability intelligence
- Risk assessment & exploitation conditions
- Attack chain visualization
- Remediation with exact patch versions
- Threat intelligence from 22 sources
- Personal watchlist & email alerts
No credit card · 7-day full trial
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires a local interactive session on the Windows host running hMailServer 6.0.0 through 6.3.3; the attacker then invokes the COM method Utilities.BlowfishDecrypt, which performs no authentication and needs no hMailServer account, passing a hexadecimal string longer than the fixed 255-byte heap buffer. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | This is a genuine but access-gated privilege-escalation/DoS issue rather than a remotely-wormable emergency. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Upgrade to hMailServer 6.3.4 or later, which is the vendor-released patch containing the fix (release: https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.4; commit: https://gitlab.com/hmailserver/hmailserver/-/commit/135a1908ff820ed587d5f180f98c53bd010d8931; tracking issue: https://gitlab.com/hmailserver/hmailserver/-/work_items/49). … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, inventory every Windows host running hMailServer and confirm which are on versions 6.0.0 through 6.3.3 (check the hMailServer Administrator console or the hMailServer.exe file version), flag any mail server where local interactive logon is broadly granted, and verify with the vendor whether hMailServer 6.3.4 - the fix referenced with commit 135a1908ff820ed587d5f180f98c53bd010d8931 - is generally released, noting that the patch status accompanying this report is recorded as not available while the advisory text cites that version. …
Sign in for detailed remediation steps and compensating controls.
Threat intelligence, references, and detailed analysis are available after sign-in.
More in Hmailserver
View allArbitrary JScript execution in Progressive Robot Ltd's hMailServer 6.0.0 through 6.3.3 on Windows lets an unauthenticate
Cross-site scripting in Progressive Robot hMailServer 6.3.2 through 6.3.5 can let a remote, unauthenticated attacker exe
Incorrect default permissions in the Windows installer for Progressive Robot hMailServer 6.0.0 through 6.3.5 let any loc
Local privilege escalation in hMailServer 6.0.0 through 6.3.5 on Windows allows an authenticated local user-one with an
Local privilege escalation in Progressive Robot hMailServer 6.3.4 and 6.3.5 on Linux allows an attacker who already has
Denial of service in Progressive Robot hMailServer 6.3.4 and 6.3.5 lets a remote unauthenticated attacker stall mail del
Denial of service in Progressive Robot hMailServer 6.0.0 through 6.3.5 lets a remote unauthenticated attacker stall mail
Denial of service in Progressive Robot hMailServer 6.0.0 through 6.3.5 allows a remote unauthenticated attacker to make
Denial of service in hMailServer arises from quadratic-time parsing of JSON objects: the reader preserved the first inst
Unauthenticated network-based denial of service in the Linux builds of Progressive Robot hMailServer 6.3.0 through 6.3.5
DNS rebinding against Progressive Robot hMailServer 6.0.0 through 6.3.5 allows a remote, unauthenticated attacker to bru
Outbound SMTP delivery in Progressive Robot hMailServer 6.0.0 through 6.3.5 fails open when DANE (RFC 7672) validation c
Same weakness CWE-122 – Heap-based Buffer Overflow
View allShare
External POC / Exploit Code
Leaving vuln.today