TI-2026-78531 Aliases CVE-2026-113728

Server-side request forgery in Bulwark Webmail via DNS rebinding

LOW 39CWE-918Published 2026-10-20 · Updated 2026-10-27

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Impact type: Information disclosure
Confidentiality · integrity · availability: High · None · None
Fix status: Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-918 and the CVSS impact.

Summary

Bulwark Webmail before 1.9.2, a self-hosted webmail client for Stalwart Mail Server, contains a flaw. The unauthenticated POST /api/fetch-ical endpoint checks a caller-supplied hostname with one DNS lookup, then fetches the URL with a second lookup. This check-then-fetch flaw enables server-side request forgery (CWE-918). A remote attacker who controls authoritative DNS can rebind the hostname to a loopback, private, link-local, or cloud metadata address, causing the server to return up to 10 MB of the internal HTTP or HTTPS response.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

Description from the CNA

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00507 43rd percentileScored 2026-11-07

Fix Fixed webmail (bulwarkmail): 1.9.2

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: Yes
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
bulwarkmail	webmail	before 1.9.2	1.9.2	Patch available	CNA

webmail Vendorbulwarkmail Affected before 1.9.2 Fixed in 1.9.2 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPE	Versions	Role	Vendor
cpe:2.3:a:bulwarkmail:webmail::::::::	—	—	bulwarkmail

cpe:2.3:a:bulwarkmail:webmail:*:*:*:*:*:*:*:* Versions — — ·bulwarkmail

Remediation

Upgrade Bulwark Webmail to version 1.9.2, which fixes this issue.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

Fix · CNA webmail (bulwarkmail) Fixed in 1.9.2

Timeline

2026-10-21 Threatist record created from CVE-2026-113728
2026-10-22 Priority changed: MEDIUM → LOW
2026-10-27 CISA SSVC decision points changed

References

Other 3

TI-2026-27078 Bulwark Webmail: Authentication Bypass in verifyIdentity() due to missing cookie validation CVSS 4.0HIGH 8.7
TI-2026-27077 Bulwark Webmail: Information Exposure: password returned in /api/auth/session CVSS 4.0HIGH 8.7
TI-2026-27527 Bulwark Webmail getClientIP() trusted client-controlled X-Forwarded-For value, enabling… CVSS 4.0HIGH 8.7
TI-2026-27525 Bulwark Webmail S/MIME signature verification accepted self-signed certificates CVSS 4.0HIGH 8.7
TI-2026-27526 Content-Security-Policy was set to Report-Only mode, failing to block XSS attacks CVSS 4.0MEDIUM 5.3

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences