Bulwark Mail Bulwark Webmail up to 1.9.1 DNS Lookup /api/fetch-ical confused deputy

Summaryinfo

A vulnerability classified as problematic was found in Bulwark Mail Bulwark Webmail up to 1.9.1. Affected is an unknown function of the file /api/fetch-ical of the component DNS Lookup. Such manipulation leads to confused deputy. This vulnerability is documented as CVE-2026-113728. The attack can be executed remotely. There is not any exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in Bulwark Mail Bulwark Webmail up to 1.9.1. Affected by this issue is an unknown function of the file /api/fetch-ical of the component DNS Lookup. The manipulation with an unknown input leads to a confused deputy vulnerability. Using CWE to declare the problem leads to CWE-441. The product receives a request, message, or directive from an upstream component, but the product does not sufficiently preserve the original source of the request before forwarding the request to an external actor that is outside of the product's control sphere. This causes the product to appear to be the source of the request, leading it to act as a proxy or other intermediary between the upstream component and the external actor. Impacted is confidentiality. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-113728 since 10/20/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. There are known technical details, but no exploit is available.

Upgrading to version 1.9.2 eliminates this vulnerability.

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Productinfo

Vendor

• Bulwark Mail

Name

• Bulwark Webmail

Version

• 1.9.0
• 1.9.1

CPE 2.3info

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CPE 2.2info

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