CVE Explorer
CVE-2026-28759
Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to validate that a remote cluster has access to a channel before processing membership removal requests during shared channel membership sync, which allows a malicious remote cluster to remove any user from any channel, including private channels, via crafted membership sync messages targeting channels the remote cluster is not authorized to access. Mattermost Advisory ID: MMSA-2026-00576
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":"11.5.1","status":"affected","version":"11.5.0","versionType":"semver"},{"lessThanOrEqual":"10.11.13","status":"affected","version":"10.11.0","versionType":"semver"},{"lessThanOrEqual":"11.4.3","status":"affected","version":"11.4.0","versionType":"semver"},{"status":"unaffected","version":"11.6.0"},{"status":"unaffected","version":"11.5.2"},{"status":"unaffected","version":"10.11.14"},{"status":"unaffected","version":"11.4.4"}]}
- cve_program_cvelist_v5affectedurn:baitaphish:normalized-source-record:v2:050ec6fefb32e638f092b4a715d98f647f8165634501048f685de82f38be88d1 · sha256:6fadcbbc4d950cb2… · /containers/cna/affected/0
Provider-owned CVSS observations
1 source assertion{"metric":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":4.3,"baseSeverity":"MEDIUM","confidentialityImpact":"NONE","integrityImpact":"LOW","privilegesRequired":"LOW","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N","version":"3.1"},"metric_type":"cvssV3_1"}
- cve_program_cvelist_v5cvssurn:baitaphish:normalized-source-record:v2:050ec6fefb32e638f092b4a715d98f647f8165634501048f685de82f38be88d1 · sha256:6fadcbbc4d950cb2… · /containers/cna/metrics/0/cvssV3_1
CWE assertions
1 source assertion{"cweId":"CWE-863","description":"CWE-863: Incorrect Authorization","lang":"en","type":"CWE"}
- cve_program_cvelist_v5cweurn:baitaphish:normalized-source-record:v2:050ec6fefb32e638f092b4a715d98f647f8165634501048f685de82f38be88d1 · sha256:6fadcbbc4d950cb2… · /containers/cna/problemTypes/0/descriptions/0
Source references
1 source assertion{"name":"MMSA-2026-00576","tags":["vendor-advisory"],"url":"https://mattermost.com/security-updates"}
- cve_program_cvelist_v5referenceurn:baitaphish:normalized-source-record:v2:050ec6fefb32e638f092b4a715d98f647f8165634501048f685de82f38be88d1 · sha256:6fadcbbc4d950cb2… · /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.