# CVE-2026-35390: Content-Security-Policy was set to Report-Only mode, failing to block XSS attacks

> Attackers can execute arbitrary JavaScript via crafted emails because the Content-Security-Policy was set to Report-Only mode, allowing session theft.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 6 Apr 2026
- **Updated:** 7 Apr 2026
- **Also known as:** GHSA-6q52-98cr-qx65

## What is CVE-2026-35390?

CVE-2026-35390 is a medium-severity cross-site scripting vulnerability in bulwarkmail webmail, published on 6 Apr 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Bulwark Webmail is a self-hosted webmail client for Stalwart Mail Server. Prior to 1.4.11, the reverse proxy (proxy.ts) set the Content-Security-Policy-Report-Only header instead of the enforcing Content-Security-Policy header. This means cross-site scripting (XSS) attacks were logged but not blocked. Any user who could inject script content (e.g., via crafted email HTML) could execute arbitrary JavaScript in the context of the application, potentially stealing session tokens or performing actions on behalf of the user. This vulnerability is fixed in 1.4.11.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-35390?

It affects 1 product.


Products: Bulwarkmail Webmail.

## How do I fix CVE-2026-35390?

No fix has been published for CVE-2026-35390 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-35390 being exploited?

There is no known exploitation of CVE-2026-35390 in the wild and no public exploit code.

## Other vulnerabilities in bulwarkmail webmail

- [CVE-2026-35389](https://insights.sbomify.com/CVE-2026-35389/): Bulwark Webmail S/MIME signature verification accepted self-signed certificates (high 8.7)
- [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)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-35390 and fix it if it is affected.

What it is: CVE-2026-35390 is a medium-severity cross-site scripting vulnerability in bulwarkmail webmail, published on 6 Apr 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-35390 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-2026-35390/ (Markdown: https://insights.sbomify.com/CVE-2026-35390/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-35390
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-35390
- OSV: https://osv.dev/vulnerability/CVE-2026-35390

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-35390/
Summaries are generated and may contain mistakes; the official description above is the record.