Server-Side Request Forgery in Mailpit Email Testing Tool
CVE-2026-21859

5.8MEDIUM

Key Information:

Vendor

Axllent

Status
Mailpit
Vendor
CVE Published:
7 January 2026

What is CVE-2026-21859?

Mailpit, a popular email testing tool used by developers, has a vulnerability in its /proxy endpoint that allows attackers to exploit Server-Side Request Forgery (SSRF). This flaw exists in versions up to 1.28.0, where the endpoint fails to block internal IP addresses after validating http:// and https:// schemes. Consequently, attackers can gain unauthorized access to internal services and APIs via HTTP GET requests with minimal headers. The vulnerability has been resolved in version 1.28.1, and users are advised to update promptly to safeguard their networks.

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Deploy the Patch

Affected Version(s)

mailpit < 1.28.1

References

https://github.com/axllent/mailpit/security/advisories/GH...
x_refsource_CONFIRM
https://github.com/axllent/mailpit/commit/3b9b470c093b3d2...
x_refsource_MISC

CVSS V3.1

Score:
5.8
Severity:
MEDIUM
Confidentiality:
Low
Integrity:
None
Availability:
Low
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Changed

Timeline

  • Vulnerability published

  • Vulnerability Reserved

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