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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

PUBLISHED Reserved 2026-02-13 | Published 2026-03-16 | Updated 2026-03-16 | Assigner Mattermost




MEDIUM: 4.3CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Problem types

CWE-918: Server-Side Request Forgery (SSRF)

Product status

Default status
unaffected

11.3.0 (semver)
affected

11.2.0 (semver)
affected

10.11.0 (semver)
affected

11.4.0
unaffected

11.3.1
unaffected

11.2.3
unaffected

10.11.11
unaffected

Credits

winfunc finder

References

mattermost.com/security-updates (MMSA-2026-00585) vendor-advisory

cve.org (CVE-2026-2455)

nvd.nist.gov (CVE-2026-2455)

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