{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-26233", "assignerOrgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee", "state": "PUBLISHED", "assignerShortName": "Mattermost", "dateReserved": "2026-02-23T22:18:41.232Z", "datePublished": "2026-03-25T16:24:47.694Z", "dateUpdated": "2026-03-25T16:24:47.694Z"}, "containers": {"cna": {"affected": [{"defaultStatus": "unaffected", "product": "Mattermost", "vendor": "Mattermost", "versions": [{"lessThanOrEqual": "11.4.0", "status": "affected", "version": "11.4.0", "versionType": "semver"}, {"lessThanOrEqual": "11.3.1", "status": "affected", "version": "11.3.0", "versionType": "semver"}, {"lessThanOrEqual": "11.2.3", "status": "affected", "version": "11.2.0", "versionType": "semver"}, {"lessThanOrEqual": "10.11.11", "status": "affected", "version": "10.11.0", "versionType": "semver"}, {"version": "11.5.0", "status": "unaffected"}, {"version": "11.4.1", "status": "unaffected"}, {"version": "11.3.2", "status": "unaffected"}, {"version": "11.2.4", "status": "unaffected"}, {"version": "10.11.12", "status": "unaffected"}]}], "credits": [{"lang": "en", "type": "finder", "value": "Axel Larsson & Jakob Ristner"}], "descriptions": [{"lang": "en", "value": "Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to rate limit login requests which allows unauthenticated remote attackers to cause denial of service (server crash and restart) via HTTP/2 single packet attack with 100+ parallel login requests.. Mattermost Advisory ID: MMSA-2025-00566"}], "metrics": [{"cvssV3_1": {"attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "LOW", "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L", "baseSeverity": "MEDIUM", "baseScore": 4.3}, "format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "description": "CWE-400 Uncontrolled Resource Consumption", "cweId": "CWE-400"}]}], "references": [{"url": "https://mattermost.com/security-updates", "name": "MMSA-2025-00566", "tags": ["vendor-advisory"]}], "solutions": [{"value": "Update Mattermost to versions 11.5.0, 11.4.1, 11.3.2, 11.2.4, 10.11.12 or higher.", "lang": "en"}], "source": {"advisory": "MMSA-2025-00566", "defect": ["https://mattermost.atlassian.net/browse/MM-66885"], "discovery": "EXTERNAL"}, "title": "Denial of Service via HTTP/2 single packet attack on login endpoint", "providerMetadata": {"orgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee", "shortName": "Mattermost", "dateUpdated": "2026-03-25T16:24:47.694Z"}, "x_generator": {"engine": "cvelib 1.8.0"}}}}

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{"cveTags": [], "descriptions": [{"lang": "en", "value": "Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to rate limit login requests which allows unauthenticated remote attackers to cause denial of service (server crash and restart) via HTTP/2 single packet attack with 100+ parallel login requests.. Mattermost Advisory ID: MMSA-2025-00566"}], "id": "CVE-2026-26233", "lastModified": "2026-03-25T17:16:53.143", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "LOW", "baseScore": 4.3, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 1.4, "source": "responsibledisclosure@mattermost.com", "type": "Secondary"}]}, "published": "2026-03-25T17:16:53.143", "references": [{"source": "responsibledisclosure@mattermost.com", "url": "https://mattermost.com/security-updates"}], "sourceIdentifier": "responsibledisclosure@mattermost.com", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-400"}], "source": "responsibledisclosure@mattermost.com", "type": "Secondary"}]}

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