CVE-2026-45713 Mailpit: Unauthenticated remote memory-exhaustion DoS via unlimited SMTP DATA and /api/v1/send body sizes
Unauthenticated attackers can cause denial of service in Mailpit by sending unlimited SMTP or HTTP payloads, exhausting system memory.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-45713?
CVE-2026-45713 is a high-severity denial of service vulnerability in axllent mailpit, published on 20 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2026-45713?
3 open source packages ship an affected version, including github.com/axllent/mailpit. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/axllent/mailpit Go | All versions | 1.30.0 |
github.com/axllent/mailpit Go | All versions | 1.30.0 |
github.com/axllent/mailpit Go | All versions | 1.30.0 |
Products include Axllent Mailpit.
How do I fix CVE-2026-45713?
Upgrade github.com/axllent/mailpit to 1.30.0 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-45713 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-45713 exists.
Other vulnerabilities in axllent mailpit
- CVE-2026-22689 Mailpit is vulnerable to Cross-Site WebSocket Hijacking (CSWSH) allowing unauthenticated access to emails
- CVE-2026-45711 Mailpit: Path traversal & arbitrary file write in mailpit dump --http via attacker-controlled message IDs
- CVE-2026-45712 Mailpit: Concurrent map read & write in proxy CSS rewriter - remote unauth crash (fatal error: concurrent map read and map write)
- CVE-2026-45709 Mailpit has an incomplete fix for GHSA-6jxm: HTML check still permits SSRF to private/loopback/IMDS via missing IP-filter dialer
- CVE-2026-27808 Mailpit is Vulnerable to Server-Side Request Forgery (SSRF) via Link Check API
Sources
Also known as GHSA-fpxj-m5q8-fphw, GO-2026-5376.