What’s Vulnerable › Vulnerabilities

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

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-20 · updated 2026-10-27
• Weakness: CWE-918

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

• bulwarkmail webmail: before 1.9.2

References

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

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