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GHSA-8r89-8w26-cq32
GHSA-8r89-8w26-cq32

Author: advisory-database[bot]

advisories/github-reviewed/2026/05/GHSA-8r89-8w26-cq32/GHSA-8r89-8w26-cq32.json

@@ -0,0 +1,103 @@
+{
+  "schema_version": "1.4.0",
+  "id": "GHSA-8r89-8w26-cq32",
+  "modified": "2026-06-01T15:27:00Z",
+  "published": "2026-05-18T09:31:48Z",
+  "aliases": [
+    "CVE-2026-5163"
+  ],
+  "summary": "Mattermost doesn't verify channel membership when processing AI-assisted message rewrites",
+  "details": "Mattermost versions 11.5.x <= 11.5.1 fail to verify channel membership when processing AI-assisted message rewrites which allows an authenticated attacker to read the content of threads in private channels and direct messages they do not have access to via a crafted request to the post rewrite endpoint.. Mattermost Advisory ID: MMSA-2026-00645",
+  "severity": [
+    {
+      "type": "CVSS_V3",
+      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N"
+    }
+  ],
+  "affected": [
+    {
+      "package": {
+        "ecosystem": "Go",
+        "name": "github.com/mattermost/mattermost/server/v8"
+      },
+      "ranges": [
+        {
+          "type": "ECOSYSTEM",
+          "events": [
+            {
+              "introduced": "11.5.0"
+            },
+            {
+              "fixed": "11.5.2"
+            }
+          ]
+        }
+      ]
+    },
+    {
+      "package": {
+        "ecosystem": "Go",
+        "name": "github.com/mattermost/mattermost/server/v8"
+      },
+      "ranges": [
+        {
+          "type": "ECOSYSTEM",
+          "events": [
+            {
+              "introduced": "0"
+            },
+            {
+              "fixed": "8.0.0-20260401090745-f4d1abe7e8f5"
+            }
+          ]
+        }
+      ]
+    },
+    {
+      "package": {
+        "ecosystem": "Go",
+        "name": "github.com/mattermost/mattermost-server"
+      },
+      "ranges": [
+        {
+          "type": "ECOSYSTEM",
+          "events": [
+            {
+              "introduced": "0"
+            },
+            {
+              "fixed": "5.3.2-0.20260401090745-f4d1abe7e8f5"
+            }
+          ]
+        }
+      ]
+    }
+  ],
+  "references": [
+    {
+      "type": "ADVISORY",
+      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-5163"
+    },
+    {
+      "type": "WEB",
+      "url": "https://github.com/mattermost/mattermost/commit/f4d1abe7e8f545f1a87f463fa9fe451c731aebf8"
+    },
+    {
+      "type": "PACKAGE",
+      "url": "https://github.com/mattermost/mattermost"
+    },
+    {
+      "type": "WEB",
+      "url": "https://mattermost.com/security-updates"
+    }
+  ],
+  "database_specific": {
+    "cwe_ids": [
+      "CWE-862"
+    ],
+    "severity": "MODERATE",
+    "github_reviewed": true,
+    "github_reviewed_at": "2026-06-01T15:27:00Z",
+    "nvd_published_at": "2026-05-18T09:16:23Z"
+  }
+}