CVE-2026-113728 Bulwark Webmail: DNS-rebinding SSRF in public iCalendar fetch endpoint
- Exploited in the wild
- Not known
- Fix
- None listed
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
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.
Sources
Also known as GHSA-24w9-8r42-8jwm.