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CVE-2026-2748— S/MIME Certificate Subject Whitespace

Quick assessment

Affected
SEPPmail Secure Email Gateway
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

SEPPmail Secure Email Gateway是德国SEPPmail公司的一个电子邮件安全网关。 SEPPmail Secure Email Gateway 15.0.1之前版本存在安全漏洞，该漏洞源于S/MIME证书验证不当，可能导致签名伪造。

AI Predicted 7.5 Difficulty: Moderate EPSS 0.20% · P8

Possible ATT&CK Techniques 1 AI

T1556 · Modify Authentication Process
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I. Basic Information for CVE-2026-2748

Vulnerability Information
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Vulnerability Title
S/MIME Certificate Subject Whitespace
Source: CVE Program / CVE List V5
Vulnerability Description
SEPPmail Secure Email Gateway before version 15.0.1 improperly validates S/MIME certificates issued for email addresses containing whitespaces, allowing signature spoofing.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:H/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
证书验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
SEPPmail Secure Email Gateway 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
SEPPmail Secure Email Gateway是德国SEPPmail公司的一个电子邮件安全网关。 SEPPmail Secure Email Gateway 15.0.1之前版本存在安全漏洞，该漏洞源于S/MIME证书验证不当，可能导致签名伪造。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
SEPPmail Secure Email Gateway 0 ~ 15.0.1 -

II. Public POCs for CVE-2026-2748

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III. Intelligence Information for CVE-2026-2748

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Other References for CVE-2026-2748 (1)

Same Patch Batch · SEPPmail · 2026-03-04 · 8 CVEs total

CVE-2026-27441 PDF Password CMDi
CVE-2026-27444 Header Email Address Parsing
CVE-2026-27442 zip_attachments Path Traversal
CVE-2026-27443 S/MIME Decryption Tag Sanitization Bypass
CVE-2026-27445 PGP Signature Reflection
CVE-2026-2746 Missing PGP Signature Tag
CVE-2026-2747 PGP Mixed Plaintext and Encrypted Content

IV. Related Vulnerabilities

Same product: Secure Email Gateway
Same vendor: SEPPmail
Same weakness: CWE-295

V. Comments for CVE-2026-2748

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