What is CVE-2026-35389?

CVE-2026-35389 is a high-severity vulnerability in Bulwarkmail Webmail, classified under Improper Certificate Validation. CVSS score: 7.5/10. Published 2026-04-06.

How severe is CVE-2026-35389?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Bulwarkmail Webmail

CVE-2026-35389

Bulwark Webmail is a self-hosted webmail client for Stalwart Mail Server. Prior to 1.4.11, S/MIME signature verification did not validate the certificate trust chain (checkChain: false). Any email signed with a self-signed or untrusted certificate was displayed as having a valid signature. This vulnerability is fixed in 1.4.11.

Vulnerability class: Improper Certificate Validation

Published 2026-04-06 · last modified 2026-07-24.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.

EPSS exploit prediction

EPSS: 0.002 (13.1th percentile), scored 2026-10-01.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 13th percentile — 13.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: +0.001

Affected products

Bulwarkmail Webmail — versions < 1.4.11

Weakness classification (CWE)

CWE-295 — Improper Certificate Validation

References

github.com/bulwarkmail/webmail/security/advisories/GHSA-v6w6-338p-p256 (Vendor Advisory)

Frequently asked questions

What is CVE-2026-35389?: CVE-2026-35389 is a high-severity vulnerability in Bulwarkmail Webmail, classified under Improper Certificate Validation. CVSS score: 7.5/10. Published 2026-04-06.
How severe is CVE-2026-35389?: High severity. CVSS v3 base score is 7.5 out of 10.