CVE-2026-21859

Name: CVE-2026-21859
Creator: NVD / NIST
Published: 2026-01-08T00:16:00.15+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 5.3/10EPSS 0.76%

Last modified Jun 17, 2026

CVE-2026-21859 is a medium-severity vulnerability rated 5.3/10 on the CVSS scale. Mailpit is an email testing tool and API for developers. Versions 1.28.0 and below have a Server-Side Request Forgery (SSRF) vulnerability in the /proxy endpoint, allowing attackers to make requests to internal network resources. EPSS estimates a 0.76% chance of exploitation in the next 30 days.

Description

Mailpit is an email testing tool and API for developers. Versions 1.28.0 and below have a Server-Side Request Forgery (SSRF) vulnerability in the /proxy endpoint, allowing attackers to make requests to internal network resources. The /proxy endpoint validates http:// and https:// schemes, but it does not block internal IP addresses, enabling attackers to access internal services and APIs. This vulnerability is limited to HTTP GET requests with minimal headers. The issue is fixed in version 1.28.1.

Metrics

CVSS 3.1

5.3/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

EPSS Probability

0.76%

50.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-918

Affected Software

Vendor	Product	Versions
Axllent	Mailpit	< 1.28.1

References

https://github.com/axllent/mailpit/commit/3b9b470c093b3d20b7d751722c1c24f3eed2e19dPatch
https://github.com/axllent/mailpit/security/advisories/GHSA-8v65-47jx-7mfrExploit, Vendor Advisory
https://github.com/axllent/mailpit/security/advisories/GHSA-8v65-47jx-7mfrExploit, Vendor Advisory

Timeline

Published: Jan 8, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-21859?

How severe is CVE-2026-21859?

CVE-2026-21859 has a CVSS score of 5.3/10 (MEDIUM severity). The EPSS model estimates a 0.76% probability of exploitation in the next 30 days.

How do I fix CVE-2026-21859?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-21859?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST