CVE-2026-35389Network attack vector

Email authenticity spoofing via disabled trust-chain validation

Published Apr 6, 2026 · Updated Apr 6, 2026

Improper certificate validation in Bulwark Webmail before 1.4.11 allows remote attackers to spoof a valid S/MIME signature on email. The S/MIME verifier in lib/smime/smime-verify.ts passes checkChain as false, accepting self-signed or otherwise untrusted signer certificates without validating their trust chain. Exposure is limited to users of S/MIME signature verification; the false valid-status indicator undermines message-authenticity decisions but does not disclose data or interrupt service.

CVSS severity8.7
High
EPSS probability0.18%
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 Bulwark Webmail before 1.4.11 allows remote attackers to spoof a valid S/MIME signature on email. The S/MIME verifier in lib/smime/smime-verify.ts passes checkChain as false, accepting self-signed or otherwise untrusted signer certificates without validating their trust chain. Exposure is limited to users of S/MIME signature verification; the false valid-status indicator undermines message-authenticity decisions but does not disclose data or interrupt service.

The record

CVE
CVE-2026-35389
Published
Apr 6, 2026
Updated
Apr 6, 2026
Vendor
Bulwark Mail
Product
Bulwark Webmail
Classifications
CWE-295, T1036
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 6, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 6, 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=< 1.4.11

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Bulwark Mail · Bulwark Webmailversion=< 1.4.11

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
8.7GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/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.

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

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
T1036Masquerading

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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