CVE-2026-2455

Name: CVE-2026-2455
Creator: NVD / NIST
Published: 2026-03-16T15:16:22.277+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 4.3/10EPSS 0.17%

Last modified Jun 17, 2026

CVE-2026-2455 is a medium-severity vulnerability rated 4.3/10 on the CVSS scale. Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to canonicalize IPv4-mapped IPv6 addresses before reserved IP validation which allows an attacker to perform SSRF attacks against internal services via IPv4-mapped IPv6 literals (e.g., [::ffff:127.0.0.1]).. Mattermost Advisory ID: MMSA-2026-00585. EPSS estimates a 0.17% chance of exploitation in the next 30 days.

Description

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to canonicalize IPv4-mapped IPv6 addresses before reserved IP validation which allows an attacker to perform SSRF attacks against internal services via IPv4-mapped IPv6 literals (e.g., [::ffff:127.0.0.1]).. Mattermost Advisory ID: MMSA-2026-00585

Metrics

CVSS 3.1

4.3/10

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

EPSS Probability

0.17%

6.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-918

Affected Software

Vendor	Product	Versions
Mattermost	Mattermost Server	>= 10.11.0, < 10.11.11
Mattermost	Mattermost Server	>= 11.2.0, < 11.2.3
Mattermost	Mattermost Server	>= 11.3.0, < 11.3.1

References

https://mattermost.com/security-updatesVendor Advisory

Timeline

Published: Mar 16, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-2455?

How severe is CVE-2026-2455?

CVE-2026-2455 has a CVSS score of 4.3/10 (MEDIUM severity). The EPSS model estimates a 0.17% probability of exploitation in the next 30 days.

How do I fix CVE-2026-2455?

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-2026-2455?

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

Scan your code now

Source: NVD / NIST