CVE-2026-2455

CWE-918 — Server-Side Request Forgery (SSRF)6 documents5 sources
Severity
4.3MEDIUM
EPSS
0.0%
top 91.53%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
4
Github.com Mattermost/mattermost-serverGithub.com Mattermost/mattermost/server/v8Mattermost Mattermost Server+1 more
Timeline
PublishedMar 16
Latest updateMar 23

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

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:NExploitability: 2.8 | Impact: 1.4

Affected Packages4 packages

▶NVDmattermost/mattermost_server10.11.0 — 10.11.11+2
▶Gogithub.com/mattermost/mattermost-server10.11.0-rc1+incompatible — 10.11.11+incompatible+6
▶Gogithub.com/mattermost/mattermost/server/v8< 8.0.0-20260129133647-5d787969c2d5
▶CVEListV5mattermost/mattermost11.3.0 — 11.3.0+2

🔴Vulnerability Details

4
OSV
Mattermost fails to canonicalize IPv4-mapped IPv6 addresses before reserved IP validation in github.com/mattermost/mattermost-server↗2026-03-23
▶
GHSA
Mattermost fails to canonicalize IPv4-mapped IPv6 addresses before reserved IP validation↗2026-03-16
▶
CVEList
SSRF bypass via IPv4-mapped IPv6 literals↗2026-03-16
▶
OSV
Mattermost fails to canonicalize IPv4-mapped IPv6 addresses before reserved IP validation↗2026-03-16
▶

🕵️Threat Intelligence

1
Wiz
CVE-2026-2455 Impact, Exploitability, and Mitigation Steps | Wiz↗
▶
CVE-2026-2455 (MEDIUM CVSS 4.3) | Mattermost versions 11.3.x <= 11.3. | cvebase.io