CVE Explorer
CVE-2026-5740
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
Known exploited
Not asserted
Disputed
No
Stale source
No
Conflicts
0
Affected products and versions
1 source assertion{"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"},{"status":"unaffected","version":"11.7.0"},{"status":"unaffected","version":"11.6.1"},{"status":"unaffected","version":"11.5.4"},{"status":"unaffe…
- cve_program_cvelist_v5affectedurn:baitaphish:normalized-source-record:v2:4b49fa7f99317b780d62b30f39d6e44cc9dcc0a3ae5c50a57f1a2171acf73f3e · sha256:fc436e4e7bd285fe… · /containers/cna/affected/0
Provider-owned CVSS observations
1 source assertion{"metric":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":7.5,"baseSeverity":"HIGH","confidentialityImpact":"NONE","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","version":"3.1"},"metric_type":"cvssV3_1"}
- cve_program_cvelist_v5cvssurn:baitaphish:normalized-source-record:v2:4b49fa7f99317b780d62b30f39d6e44cc9dcc0a3ae5c50a57f1a2171acf73f3e · sha256:fc436e4e7bd285fe… · /containers/cna/metrics/0/cvssV3_1
CWE assertions
1 source assertion{"cweId":"CWE-789","description":"CWE-789: Memory Allocation with Excessive Size Value","lang":"en","type":"CWE"}
- cve_program_cvelist_v5cweurn:baitaphish:normalized-source-record:v2:4b49fa7f99317b780d62b30f39d6e44cc9dcc0a3ae5c50a57f1a2171acf73f3e · sha256:fc436e4e7bd285fe… · /containers/cna/problemTypes/0/descriptions/0
Source references
1 source assertion{"name":"MMSA-2026-00647","tags":["vendor-advisory"],"url":"https://mattermost.com/security-updates"}
- cve_program_cvelist_v5referenceurn:baitaphish:normalized-source-record:v2:4b49fa7f99317b780d62b30f39d6e44cc9dcc0a3ae5c50a57f1a2171acf73f3e · sha256:fc436e4e7bd285fe… · /containers/cna/references/0
Attribution and limitations
- CVE Program CVEList V5: Reproduce the MITRE copyright designation and CVE license in copies. Source →
Provider severity values are preserved separately. Baitaphish does not convert them into a risk rating, infer affected products, or treat EPSS as observed exploitation.