Vulnerability · Published Oct 20, 2026 · Assigned by GitHub_M

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

High 7.5

In plain English

A high-severity server-side request forgery in webmail from bulwarkmail. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 43% of all known vulnerabilities).

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.5%top 56.5% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

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.

Affected products (as reported)

Vendor	Product	Versions
bulwarkmail	webmail	< 1.9.2

Weakness: CWE-918 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

References

https://github.com/bulwarkmail/webmail/security/advisories/GHSA-24w9-8r42-8jwm x_refsource_CONFIRM
https://github.com/bulwarkmail/webmail/commit/3288589e5248dcc1da769cc578827a9ee1adc941 x_refsource_MISC
https://github.com/bulwarkmail/webmail/releases/tag/1.9.2 x_refsource_MISC