{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-5740", "assignerOrgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee", "state": "PUBLISHED", "assignerShortName": "Mattermost", "dateReserved": "2026-04-07T13:39:34.067Z", "datePublished": "2026-05-22T10:22:01.030Z", "dateUpdated": "2026-05-22T12:14:25.145Z"}, "containers": {"cna": {"affected": [{"defaultStatus": "unaffected", "product": "Mattermost", "vendor": "Mattermost", "versions": [{"lessThanOrEqual": "11.6.0", "status": "affected", "version": "11.6.0", "versionType": "semver"}, {"lessThanOrEqual": "11.5.3", "status": "affected", "version": "11.5.0", "versionType": "semver"}, {"lessThanOrEqual": "11.4.4", "status": "affected", "version": "11.4.0", "versionType": "semver"}, {"lessThanOrEqual": "10.11.14", "status": "affected", "version": "10.11.0", "versionType": "semver"}, {"version": "11.7.0", "status": "unaffected"}, {"version": "11.6.1", "status": "unaffected"}, {"version": "11.5.4", "status": "unaffected"}, {"version": "11.4.5", "status": "unaffected"}, {"version": "10.11.15", "status": "unaffected"}]}], "credits": [{"lang": "en", "type": "finder", "value": "ZephrFish"}], "descriptions": [{"lang": "en", "value": "Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to properly validate msgpack-encoded WebSocket frames before memory allocation which allows an unauthenticated remote attacker to crash the server process and cause a full service outage for all users via a crafted binary WebSocket message sent to the public WebSocket endpoint.. Mattermost Advisory ID: MMSA-2026-00647"}], "metrics": [{"cvssV3_1": {"attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH", "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseSeverity": "HIGH", "baseScore": 7.5}, "format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "description": "CWE-789: Memory Allocation with Excessive Size Value", "cweId": "CWE-789"}]}], "references": [{"url": "https://mattermost.com/security-updates", "name": "MMSA-2026-00647", "tags": ["vendor-advisory"]}], "solutions": [{"value": "Update Mattermost to versions 11.7.0, 11.6.1, 11.5.4, 11.4.5, 10.11.15 or higher.", "lang": "en"}], "source": {"advisory": "MMSA-2026-00647", "defect": ["https://mattermost.atlassian.net/browse/MM-68221"], "discovery": "EXTERNAL"}, "title": "Unauthenticated WebSocket binary frame causes denial of service in Mattermost Server", "providerMetadata": {"orgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee", "shortName": "Mattermost", "dateUpdated": "2026-05-22T10:22:01.030Z"}, "x_generator": {"engine": "cvelib 1.8.0"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-05-22T12:14:18.991826Z", "id": "CVE-2026-5740", "options": [{"Exploitation": "none"}, {"Automatable": "yes"}, {"Technical Impact": "partial"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-05-22T12:14:25.145Z"}}]}}

{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CISA ADP Vulnrichment", "metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-5740", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "yes"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2026-05-22T12:14:18.991826Z"}}}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-05-22T12:14:21.827Z"}}], "cna": {"title": "Unauthenticated WebSocket binary frame causes denial of service in Mattermost Server", "source": {"defect": ["https://mattermost.atlassian.net/browse/MM-68221"], "advisory": "MMSA-2026-00647", "discovery": "EXTERNAL"}, "credits": [{"lang": "en", "type": "finder", "value": "ZephrFish"}], "metrics": [{"format": "CVSS", "cvssV3_1": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 7.5, "attackVector": "NETWORK", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "NONE", "confidentialityImpact": "NONE"}, "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "affected": [{"vendor": "Mattermost", "product": "Mattermost", "versions": [{"status": "affected", "version": "11.6.0", "versionType": "semver", "lessThanOrEqual": "11.6.0"}, {"status": "affected", "version": "11.5.0", "versionType": "semver", "lessThanOrEqual": "11.5.3"}, {"status": "affected", "version": "11.4.0", "versionType": "semver", "lessThanOrEqual": "11.4.4"}, {"status": "affected", "version": "10.11.0", "versionType": "semver", "lessThanOrEqual": "10.11.14"}, {"status": "unaffected", "version": "11.7.0"}, {"status": "unaffected", "version": "11.6.1"}, {"status": "unaffected", "version": "11.5.4"}, {"status": "unaffected", "version": "11.4.5"}, {"status": "unaffected", "version": "10.11.15"}], "defaultStatus": "unaffected"}], "solutions": [{"lang": "en", "value": "Update Mattermost to versions 11.7.0, 11.6.1, 11.5.4, 11.4.5, 10.11.15 or higher."}], "references": [{"url": "https://mattermost.com/security-updates", "name": "MMSA-2026-00647", "tags": ["vendor-advisory"]}], "x_generator": {"engine": "cvelib 1.8.0"}, "descriptions": [{"lang": "en", "value": "Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to properly validate msgpack-encoded WebSocket frames before memory allocation which allows an unauthenticated remote attacker to crash the server process and cause a full service outage for all users via a crafted binary WebSocket message sent to the public WebSocket endpoint.. Mattermost Advisory ID: MMSA-2026-00647"}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-789", "description": "CWE-789: Memory Allocation with Excessive Size Value"}]}], "providerMetadata": {"orgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee", "shortName": "Mattermost", "dateUpdated": "2026-05-22T10:22:01.030Z"}}}, "cveMetadata": {"cveId": "CVE-2026-5740", "state": "PUBLISHED", "dateUpdated": "2026-05-22T12:14:25.145Z", "dateReserved": "2026-04-07T13:39:34.067Z", "assignerOrgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee", "datePublished": "2026-05-22T10:22:01.030Z", "assignerShortName": "Mattermost"}, "dataVersion": "5.2"}

{}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[11.6.0,11.6.0]"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[11.5.0,11.5.3]"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[11.4.0,11.4.4]"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[10.11.0,10.11.14]"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "11.7.0"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "11.6.1"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "11.5.4"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "11.4.5"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "10.11.15"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "Mattermost", "source": "cna", "vendor": "Mattermost"}, "product": "mattermost", "vendor": "mattermost"}], "created": "2026-05-22T12:30:27.479680+00:00", "updated": "2026-05-22T13:00:12.339385+00:00", "vendors": ["mattermost", "mattermost$PRODUCT$mattermost"]}