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TI-2026-19194 Aliases CVE-2026-23829GHSA-54wq-72mp-cq7c

Mailpit has SMTP Header Injection via Regex Bypass

Priority MEDIUM 63CWE-150Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
None · Low · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub.

Summary

Mailpit is an email testing tool and API for developers. Prior to version 1.28.3, Mailpit's SMTP server is vulnerable to Header Injection due to an insufficient Regular Expression used to validate `RCPT TO` and `MAIL FROM` addresses. An attacker can inject arbitrary SMTP headers (or corrupt existing ones) by including carriage return characters (`\r`) in the email address. This header injection occurs because the regex intended to filter control characters fails to exclude `\r` and `\n` when used inside a character class. Version 1.28.3 fixes this issue.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.01402 72nd percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed mailpit (axllent): 1.28.3github.com/axllent/mailpit (Go): 1.28.3

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 1.28.31.28.3Patch availableCNA
—github.com/axllent/mailpit (Go)before 1.28.31.28.3Patch availableGHSA-54wq-72mp-cq7c
  • mailpit Vendoraxllent Affected before 1.28.3 Fixed in 1.28.3 Patch available CNA
  • github.com/axllent/mailpit (Go) Vendor— Affected before 1.28.3 Fixed in 1.28.3 Patch available GHSA-54wq-72mp-cq7c

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:axllent:mailpit:*:*:*:*:*:*:*:*before 1.28.3Vulnerableaxllent
  • cpe:2.3:a:axllent:mailpit:*:*:*:*:*:*:*:* Versions before 1.28.3 Vulnerable ·axllent

Remediation

  • Fix · CNA mailpit (axllent) Fixed in 1.28.3
  • Fix · GHSA-54wq-72mp-cq7c github.com/axllent/mailpit (Go) Fixed in 1.28.3 Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-23829
  2. 2026-10-03 Alias added: GHSA-54wq-72mp-cq7c

References

Exploit 1

Patch 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-2026-33452 Mailpit: Unauthenticated remote memory-exhaustion DoS via unlimited SMTP DATA and /api/v1/send body sizes CVSS 3.1HIGH 7.5
  • 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-2026-33451 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