What’s Vulnerable › Vulnerabilities

CVE-2025-34491: GFI MailEssentials < 21.8 MultiNode Insecure Deserialization

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.9% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2025-04-28 · updated 2026-06-17
• Weakness: CWE-502

Description

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.

Affected products

• GFI Software MailEssentials AI: before 21.8 — fixed in 21.8

How to fix

Upgrade to a fixed version: GFI Software MailEssentials AI 21.8. Check the vendor advisory for mitigations.

References

• https://frycos.github.io/vulns4free/2025/04/28/mailessentials.html
• https://gfi.ai/products-and-solutions/network-security-solutions/mailessentials/resources/documentation/product-releases
• https://www.vulncheck.com/advisories/gfi-mailessentials-multinode-insecure-deserialization

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