Vulnerability 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.
CVSS Score
HIGH
Related Weaknesses (CWE)
References
- https://github.com/bulwarkmail/webmail/commit/3288589e5248dcc1da769cc578827a9ee1
- https://github.com/bulwarkmail/webmail/releases/tag/1.9.2
- https://github.com/bulwarkmail/webmail/security/advisories/GHSA-24w9-8r42-8jwm
FAQ
What is CVE-2026-113728?
CVE-2026-113728 is a vulnerability with a CVSS score of 7.5 (HIGH). 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...
How severe is CVE-2026-113728?
CVE-2026-113728 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-113728?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.