CVE-2026-45713

Mailpit is an email testing tool and API for developers. Prior to version 1.30.0, the Mailpit SMTP server has a Server.MaxSize int field that controls the maximum allowed DATA payload size, but the field is never assigned anywhere outside test code, leaving it at Go's zero value (0 ⇒ "no limit"). The same applies to the HTTP /api/v1/send endpoint, whose request body is decoded with json.NewDecoder(r.Body) and no http.MaxBytesReader. Because Mailpit's default listeners bind [::]:1025 (SMTP) and [::]:8025 (HTTP), with no authentication required on either, a single network-reachable attacker can push an arbitrarily large message into Mailpit and watch RAM consumption spike with a ~7-10× amplification factor (raw frame → enmime envelope tree → search-text index → zstd-encoded write to SQLite). Repeating the attack — or running it concurrently from multiple connections — drives the process to OOM-kill. Version 1.30.0 contains a patch.

• CWE-400
• CWE-770

• https://github.com/axllent/mailpit/releases/tag/v1.30.0Release Notes
• https://github.com/axllent/mailpit/security/advisories/GHSA-fpxj-m5q8-fphwExploit, Vendor Advisory
• https://github.com/axllent/mailpit/security/advisories/GHSA-fpxj-m5q8-fphwExploit, Vendor Advisory

Published

Jul 20, 2026

Last Modified

Jul 28, 2026

Status

Analyzed

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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