CVE-2026-2748Network attack vector

Unauthenticated signature spoofing via whitespace certificates

Published Mar 4, 2026 · Updated Mar 4, 2026

Improper certificate validation in SEPPmail Secure Email Gateway before 15.0.1 allows remote attackers to spoof S/MIME signatures. The gateway incorrectly accepts S/MIME certificates issued for email addresses containing whitespace, allowing a crafted identity to pass sender validation. No authentication or user interaction is required, and the reported consequence is forged message authenticity rather than message disclosure or service interruption.

CVSS severity5.3
Medium
EPSS probability0.12%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate validation in SEPPmail Secure Email Gateway before 15.0.1 allows remote attackers to spoof S/MIME signatures. The gateway incorrectly accepts S/MIME certificates issued for email addresses containing whitespace, allowing a crafted identity to pass sender validation. No authentication or user interaction is required, and the reported consequence is forged message authenticity rather than message disclosure or service interruption.

The record

CVE
CVE-2026-2748
Published
Mar 4, 2026
Updated
Mar 4, 2026
Vendor
SEPPmail
Product
Secure Email Gateway
Classifications
CWE-295, T1656
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 4, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 4, 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=0 <15.0.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

SEPPmail · Secure Email Gatewayversion=0 <15.0.1

Published CVSS scores

5.3NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
7.8Switzerland Government Common Vulnerability ProgramCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:H/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.

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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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-295Improper Certificate Validation
T1656Impersonation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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