# CVE-2026-35389: Bulwark Webmail S/MIME signature verification accepted self-signed certificates

> Attackers can spoof signed emails by using self-signed certificates, bypassing S/MIME signature verification in Bulwark Webmail.

- **Severity:** High 8.7 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 6 Apr 2026
- **Updated:** 7 Apr 2026
- **Also known as:** GHSA-v6w6-338p-p256

## What is CVE-2026-35389?

CVE-2026-35389 is a high-severity vulnerability in bulwarkmail webmail, published on 6 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-295 (Improper Certificate Validation)

## Which versions are affected by CVE-2026-35389?

It affects 1 product.


Products: Bulwarkmail Webmail.

## How do I fix CVE-2026-35389?

No fix has been published for CVE-2026-35389 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-35389 being exploited?

There is no known exploitation of CVE-2026-35389 in the wild and no public exploit code.

## Other vulnerabilities in bulwarkmail webmail

- [CVE-2026-35391](https://insights.sbomify.com/CVE-2026-35391/): Security feature bypass in webmail (high 8.7)
- [CVE-2026-34833](https://insights.sbomify.com/CVE-2026-34833/): Bulwark Webmail: Information Exposure: password returned in /api/auth/session (high 8.7)
- [CVE-2026-34834](https://insights.sbomify.com/CVE-2026-34834/): Bulwark Webmail: Authentication Bypass in verifyIdentity() due to missing cookie validation (high 8.7)
- [CVE-2026-35390](https://insights.sbomify.com/CVE-2026-35390/): Content-Security-Policy was set to Report-Only mode, failing to block XSS attacks (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-35389 and fix it if it is affected.

What it is: CVE-2026-35389 is a high-severity vulnerability in bulwarkmail webmail, published on 6 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-35389 in the wild and no public exploit code.

Affected product: bulwarkmail webmail. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-35389/ (Markdown: https://insights.sbomify.com/CVE-2026-35389/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-35389
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-35389
- OSV: https://osv.dev/vulnerability/CVE-2026-35389

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-35389/
Summaries are generated and may contain mistakes; the official description above is the record.