CVE-2026-2455CWE-918

SSRF bypass via IPv4-mapped IPv6 literals

Medium · published March 16, 2026

CVSS v3.1
4.3
EPSS
0%
Percentile
5.8
In the wild
Unconfirmed
What it is

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

The record
Technical detail
CVSS v3.1
4.3 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
CVSS v4.0
Not supplied
EPSS
0.00168 · 5.8th percentile
Weakness
CWE-918 · Server-Side Request Forgery (SSRF)
Published
2026-03-16T14:53Z
EPSS history
Timeline
  • 16 MAR 14:53Z
    SSRF bypass via IPv4-mapped IPv6 literals
    cvelistv5