CVE-2025-34491
Published: 28 April 2025
Summary
CVE-2025-34491 is a high-severity Deserialization of Untrusted Data (CWE-502) vulnerability in Gfi Mailessentials. Its CVSS base score is 8.8 (High).
Operationally, ranked in the top 44.0% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
Deeper analysis
GFI MailEssentials versions prior to 21.8 contain a .NET deserialization vulnerability (CWE-502) that permits remote code execution. The flaw resides in the multi-server join process, where the application accepts and processes serialized .NET objects without adequate validation.
A remote attacker who already possesses valid credentials can exploit the issue by submitting a crafted serialized object during multi-server registration. Successful exploitation grants the attacker arbitrary code execution with the privileges of the MailEssentials service, resulting in full confidentiality, integrity, and availability impact as reflected in the CVSS 8.8 score.
The vendor addressed the flaw in release 21.8, and public advisories recommend upgrading to that version or later. The accompanying documentation and third-party analyses confirm that the insecure deserialization path is removed once the update is applied.
EPSS for the CVE rose from a low baseline to a recorded peak of 0.0116 before settling at the current value of 0.0033, indicating measurable post-disclosure exploitation interest.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2025-14683
Vulnerability details
GFI MailEssentials prior to version 21.8 is vulnerable to a .NET deserialization issue. A remote and authenticated attacker can execute arbitrary code by sending crafted serialized .NET when joining to a Multi-Server setup.
- CWE(s)
Related Threats
No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.
Affected Assets
Mitigating Controls
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Penetration testing supplies malicious serialized objects, detecting unsafe deserialization and supporting corrective actions.
Evaluation of untrusted data handling (deserialization testing) reveals unsafe processing, which the required remediation process addresses.
Untrusted serialized data can be deserialized and observed inside the chamber, blocking gadget-chain exploitation outside the sandbox.
Validates or rejects untrusted serialized data before deserialization occurs.
Identifies and blocks malicious code introduced through deserialization of untrusted data at system boundaries.
Integrity verification of serialized information can detect tampering before deserialization occurs.
Provenance of associated data allows detection of untrusted sources before deserialization or processing occurs.