# CVE-2026-113728: Bulwark Webmail: DNS-rebinding SSRF in public iCalendar fetch endpoint


- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 20 Oct 2026
- **Updated:** 27 Oct 2026
- **Also known as:** GHSA-24w9-8r42-8jwm

## What is CVE-2026-113728?

CVE-2026-113728 is a high-severity vulnerability in bulwarkmail webmail, published on 20 Oct 2026. 

### Official description

Bulwark Webmail is a self-hosted webmail client for Stalwart Mail Server. Prior to 1.9.2, the unauthenticated POST /api/fetch-ical endpoint validates a caller-supplied hostname with one DNS lookup and then passes the URL to fetch, which performs a separate lookup for the socket connection. An attacker controlling authoritative DNS can return a public address during validation and then rebind the hostname to a loopback, private, link-local, or cloud metadata address for the connection, causing the server to return up to 10 MB of an internal HTTP or HTTPS response. The same check-then-fetch pattern also existed in authenticated JMAP login and TOTP token-exchange flows. This issue is fixed in version 1.9.2.

Weakness: CWE-918 (Server-Side Request Forgery)

## Which versions are affected by CVE-2026-113728?


## How do I fix CVE-2026-113728?

No fix has been published for CVE-2026-113728 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-113728 being exploited?

There is no known exploitation of CVE-2026-113728 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-113728 and fix it if it is affected.

What it is: CVE-2026-113728 is a high-severity vulnerability in bulwarkmail webmail, published on 20 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-113728 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-2026-113728/ (Markdown: https://insights.sbomify.com/CVE-2026-113728/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-113728
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-113728
- OSV: https://osv.dev/vulnerability/CVE-2026-113728

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-113728/
Summaries are generated and may contain mistakes; the official description above is the record.