Internal-service SSRF via IPv4-mapped IPv6 literals
Published Mar 16, 2026 · Updated Mar 16, 2026
SSRF in Mattermost 10.11.0 through 10.11.10, 11.2.0 through 11.2.2, and 11.3.0 allows remote authenticated users to read internal-service responses. IsReservedIP compares IPv4-mapped IPv6 values directly against reserved IPv4 ranges without converting them to native IPv4 form. Authenticated access and a feature that makes the server fetch an attacker-supplied URL are required; the documented impact is limited to reading reachable internal services.
Summary
What happened
SSRF in Mattermost 10.11.0 through 10.11.10, 11.2.0 through 11.2.2, and 11.3.0 allows remote authenticated users to read internal-service responses. IsReservedIP compares IPv4-mapped IPv6 values directly against reserved IPv4 ranges without converting them to native IPv4 form. Authenticated access and a feature that makes the server fetch an attacker-supplied URL are required; the documented impact is limited to reading reachable internal services.
The record
- CVE
- CVE-2026-2455
- Published
- Mar 16, 2026
- Updated
- Mar 16, 2026
- Vendor
- Mattermost
- Product
- Mattermost
- Classifications
- CWE-918
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Mar 16, 2026CVE publishedPublication date reported by the CVE source.
- Mar 16, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=10.11.0 <=10.11.10
- Affected versionversion=11.2.0 <=11.2.2
- Affected versionversion=11.3.0 <=11.3.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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