CVE-2025-34491Public exploitNetwork attack vector

Authenticated code execution via certificate stream deserialization

Published Apr 28, 2025 · Updated Nov 19, 2025

Unsafe .NET deserialization in GFI MailEssentials before 21.8 allows remote authenticated users to execute arbitrary code during Multi-Server joining. InstallClientCertificate copies the supplied certificate stream into memory and passes it to BinaryFormatter.Deserialize without type restrictions. Any successfully authenticated domain or local account can reach the service because the method performs no administrator authorization check, resulting in code execution on the receiving server.

CVSS severity8.8
High
EPSS probability0.88%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Unsafe .NET deserialization in GFI MailEssentials before 21.8 allows remote authenticated users to execute arbitrary code during Multi-Server joining. InstallClientCertificate copies the supplied certificate stream into memory and passes it to BinaryFormatter.Deserialize without type restrictions. Any successfully authenticated domain or local account can reach the service because the method performs no administrator authorization check, resulting in code execution on the receiving server.

The record

CVE
CVE-2025-34491
Published
Apr 28, 2025
Updated
Nov 19, 2025
Vendor
GFI Software
Product
GFI MailEssentials
Classifications
CWE-502, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 28, 2025CVE publishedPublication date reported by the CVE source.
  2. Nov 19, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <21.8

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

GFI Software · GFI MailEssentialsversion=0 <21.8

Published CVSS scores

8.8VulnCheckCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-502Deserialization of Untrusted Data
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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