CVE-2026-84465Network attack vectorHinoki check available

Sender impersonation via certificate-name trust matching

Published Sep 25, 2026 · Updated Sep 25, 2026

Improper certificate validation in Zammad before 7.1.2 allows remote attackers to impersonate trusted senders through S/MIME-signed email. The verifier treats a certificate as trusted when its subject name matches a stored certificate, without validating the presented certificate's trust chain. Exploitation requires the name of a previously trusted sender and causes forged mail to receive the same valid-signature indicator as genuine mail.

CVSS severity7.1
High
EPSS probability0.12%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
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Summary

What happened

Improper certificate validation in Zammad before 7.1.2 allows remote attackers to impersonate trusted senders through S/MIME-signed email. The verifier treats a certificate as trusted when its subject name matches a stored certificate, without validating the presented certificate's trust chain. Exploitation requires the name of a previously trusted sender and causes forged mail to receive the same valid-signature indicator as genuine mail.

The record

CVE
CVE-2026-84465
Published
Sep 25, 2026
Updated
Sep 25, 2026
Vendor
Zammad GmbH
Product
Zammad
Classifications
CWE-290, CWE-295, CWE-347, T1656
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 25, 2026Record 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=< 7.1.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Zammad GmbH · Zammadversion=< 7.1.2

Published CVSS scores

7.1ZammadCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

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.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-290Authentication Bypass by Spoofing
CWE-295Improper Certificate Validation
CWE-347Improper Verification of Cryptographic Signature
T1656Impersonation

Public exploit references

No public exploit references are available in this record.

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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