Medium 4.3Published Mar 16, 2026

CVE-2026-2455SSRF bypass via IPv4-mapped IPv6 literals

Updated under an hour ago (Oct 26, 2026, 3:00 PM ET)

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It affects Mattermost and 1 other product. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

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: 4.3 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Weakness (CWE): CWE-918
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Mattermost
NVD analysis: Analyzed
Record last updated: Mar 16, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Mattermost Mattermost mattermost:mattermost (from the name)	from 11.3.0 through 11.3.0; from 11.2.0 through 11.2.2; from 10.11.0 through 10.11.10; 11.4.0 not affected; 11.3.1 not affected; 11.2.3 not affected; 10.11.11 not affected	CNA record
mattermost mattermost_server mattermost:mattermost_server	from 10.11.0 before 10.11.11; from 11.2.0 before 11.2.3; from 11.3.0 before 11.3.1	NVD

References

References

https://mattermost.com/security-updates	vendor-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.