CVE-2026-45713 is a high-severity uncontrolled resource consumption vulnerability in github.com/axllent/mailpit (go), affecting versions < 1.30.0. It is fixed in 1.30.0.
Summary 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. Details Pre-auth, remote DoS on every Mailpit deployment running the default configuration. Memory is the primary axis; disk is a secondary one, because each oversized message is also persisted to the SQLite store (config.MaxMessages caps the count at 500 but never the bytes, so 500 attacker-sized messages × 1 GiB each = ~500 GiB on the host disk before the LRU rotates). Affected code internal/smtpd/smtpd.go:107, the field exists: internal/smtpd/smtpd.go:863-877, the enforcement is gated on > 0: internal/smtpd/main.go:223-248, the field is never populated; grep -rn "MaxSize" cmd/ config/ returns zero hits. There is no --smtp-max-message-size CLI flag, no MPSMTPMAXMESSAGESIZE env var. server/apiv1/send.go:45-52, HTTP path has the same defect: No r.Body = http.MaxBytesReader(w, r.Body, N) wrapper; server.ReadTimeout of 30 s is transmission-time, not body-size-budget. PoC Baseline RSS on a freshly-started binary: 25 MiB. After one 100 MiB SMTP DATA block: ~1 037 MiB (≈10× amplification, single connection, no auth): Equivalent over HTTP: Five concurrent SMTP connections × 50 MiB each took the same machine from 25 MiB → 1 970 MiB during the attack window. With sufficient bandwidth the only ceiling is host RAM. Impact Unauthenticated remote attackers can send arbitrarily large emails via SMTP or HTTP, causing unbounded memory and disk growth, leading to out-of-memory (OOM) kills and full Mailpit process crash (DoS)
Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.
CVE-2026-45713 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment.
A fixed version is available (1.30.0). Upgrading removes the vulnerable code path.
go
github.com/axllent/mailpit (< 1.30.0)github.com/axllent/mailpit → 1.30.0 (go)Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter instead of chasing every advisory.
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Upgrade github.com/axllent/mailpit to 1.30.0 or later to resolve this vulnerability.
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
CVE-2026-45713 is a high-severity uncontrolled resource consumption vulnerability in github.com/axllent/mailpit (go), affecting versions < 1.30.0. It is fixed in 1.30.0. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
CVE-2026-45713 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
github.com/axllent/mailpit (go) versions < 1.30.0 is affected.
Yes. CVE-2026-45713 is fixed in 1.30.0. Upgrade to this version or later.
Whether CVE-2026-45713 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
Upgrade github.com/axllent/mailpit to 1.30.0 or later.