axllent mailpit up to 1.29.1 Link Check API link-check server-side request forgery

Summaryinfo

A vulnerability classified as critical has been found in axllent mailpit up to 1.29.1. This affects an unknown part of the file /api/v1/message/{ID}/link-check of the component Link Check API. This manipulation causes server-side request forgery. The identification of this vulnerability is CVE-2026-27808. It is possible to initiate the attack remotely. There is no exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability has been found in axllent mailpit up to 1.29.1 and classified as critical. Affected by this vulnerability is some unknown processing of the file /api/v1/message/{ID}/link-check of the component Link Check API. The manipulation with an unknown input leads to a server-side request forgery vulnerability. The CWE definition for the vulnerability is CWE-918. The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

Mailpit is an email testing tool and API for developers. Prior to version 1.29.2, the Link Check API (/api/v1/message/{ID}/link-check) is vulnerable to Server-Side Request Forgery (SSRF). The server performs HTTP HEAD requests to every URL found in an email without validating target hosts or filtering private/internal IP addresses. The response returns status codes and status text per link, making this a non-blind SSRF. In the default configuration (no authentication on SMTP or API), this is fully exploitable remotely with zero user interaction. This is the same class of vulnerability that was fixed in the HTML Check API (CVE-2026-23845 / GHSA-6jxm-fv7w-rw5j) and the screenshot proxy (CVE-2026-21859 / GHSA-8v65-47jx-7mfr), but the Link Check code path was not included in either fix. Version 1.29.2 fixes this vulnerability.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-27808 since 02/24/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 1.29.2 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch 10ad4df8cc0cd9e51dea1b4410009545eef7fbf5 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at EUVD (EUVD-2026-8775) and CERT Bund (WID-SEC-2026-0537). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Affected

• Open Source MailPit

Productinfo

Vendor

• axllent

Name

• mailpit

Version

• 1.29.0
• 1.29.1

License

• open-source

Website

• Product: https://github.com/axllent/mailpit/

CPE 2.3info

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CPE 2.2info

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