CVE-2026-2455

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

Affected packages (6)

• Go/github.com/mattermost/mattermost-serverfrom 0, < 5.3.2-0.20260129133647-5d787969c2d5
• Go/github.com/mattermost/mattermost-server>= 10.11.0-rc1+incompatible, < 10.11.11+incompatible, >= 11.2.0-rc1+incompatible, < 11.2.3+incompatible, >= 11.3.0-rc1+incompatible, < 11.3.1+incompatible
• Go/github.com/mattermost/mattermost-server/v5from 0
• Go/github.com/mattermost/mattermost-server/v6from 0
• Go/github.com/mattermost/mattermost/server/v8from 0, < 8.0.0-20260129133647-5d787969c2d5
• Go/github.com/mattermost/mattermost/server/v8from 0, < 8.0.0-20260129133647-5d787969c2d5

CVSS scores

References (5)

• ADVISORYhttps://github.com/advisories/GHSA-gqv7-j2j8-qmwq
• ADVISORYhttps://nvd.nist.gov/vuln/detail/CVE-2026-2455
• PATCHhttps://github.com/mattermost/mattermost
• WEBhttps://github.com/mattermost/mattermost/commit/5d787969c2d5ab591a9dcd61b0810475eed7a646
• WEBhttps://mattermost.com/security-updates