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TI-2026-33452 Aliases CVE-2026-45713GHSA-fpxj-m5q8-fphw

Mailpit: Unauthenticated remote memory-exhaustion DoS via unlimited SMTP DATA and /api/v1/send body sizes

Priority HIGH 72CWE-400Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-400.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00607 49th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed mailpit (axllent): 1.30.0github.com/axllent/mailpit (Go): 1.30.0

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
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

VendorProductAffected versionsFixed inStatusSource
axllentmailpitbefore 1.30.01.30.0Patch availableCNA
—github.com/axllent/mailpit (Go)before 1.30.01.30.0Patch availableGHSA-fpxj-m5q8-fphw
  • mailpit Vendoraxllent Affected before 1.30.0 Fixed in 1.30.0 Patch available CNA
  • github.com/axllent/mailpit (Go) Vendor— Affected before 1.30.0 Fixed in 1.30.0 Patch available GHSA-fpxj-m5q8-fphw

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:axllent:mailpit:*:*:*:*:*:*:*:*before 1.30.0Vulnerableaxllent
  • cpe:2.3:a:axllent:mailpit:*:*:*:*:*:*:*:* Versions before 1.30.0 Vulnerable ·axllent

Remediation

  • Fix · CNA mailpit (axllent) Fixed in 1.30.0
  • Fix · GHSA-fpxj-m5q8-fphw github.com/axllent/mailpit (Go) Fixed in 1.30.0 Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-45713
  2. 2026-10-03 Alias added: GHSA-fpxj-m5q8-fphw

References

Exploit 1

Advisory 1

Other 2

  • TI-2026-22161 Mailpit is Vulnerable to Server-Side Request Forgery (SSRF) via Link Check API CVSS 3.1HIGH 8.6
  • TI-2026-33450 Mailpit: Path traversal & arbitrary file write in mailpit dump --http via attacker-controlled message IDs CVSS 3.1HIGH 8.2
  • TI-2026-17561 Mailpit Proxy Endpoint is Vulnerable to Server-Side Request Forgery (SSRF) CVSS 3.1MEDIUM 5.8
  • TI-2026-19194 Mailpit has SMTP Header Injection via Regex Bypass CVSS 3.1MEDIUM 5.3
  • TI-2026-33451 Race condition in axllent mailpit CVSS 3.1MEDIUM 5.9
  • TI-2026-19208 Mailpit Vulnerable to Server-Side Request Forgery (SSRF) via HTML Check API CVSS 3.1HIGH 7.5
See all 9 →

Sources

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