{"answers":{"affected":"9 open source packages ship an affected version, including github.com/mattermost/mattermost-server. It affects 1 product.","exploited":"There is no known exploitation of CVE-2026-3473 in the wild and no public exploit code.","fix":"Upgrade github.com/mattermost/mattermost-server to a fixed version for your release line: 10.11.15, 10.11.15+incompatible, 11.4.5+incompatible or 11.5.4+incompatible.","what":"CVE-2026-3473 is a medium-severity missing authorization vulnerability in Mattermost Mattermost Server, published on 22 May 2026. Any signed-in user can exploit it over the network, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-3473 and fix it if it is affected.\n\nWhat it is: CVE-2026-3473 is a medium-severity missing authorization vulnerability in Mattermost Mattermost Server, published on 22 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2026-3473 in the wild and no public exploit code.\n\nAffected packages and fixed versions:\n- github.com/mattermost/mattermost-server (Go): affected from 10.11.0; fixed in 10.11.15\n- github.com/mattermost/mattermost-server (Go): affected from 10.11.0; fixed in 10.11.15\n- github.com/mattermost/mattermost-server (Go): affected from 10.11.0+incompatible; fixed in 10.11.15+incompatible, 11.4.5+incompatible, 11.5.4+incompatible, 11.6.1+incompatible\n- github.com/mattermost/mattermost-server (Go): affected from 11.4.0; fixed in 11.4.5\n- github.com/mattermost/mattermost-server (Go): affected from 11.4.0; fixed in 11.4.5\n- github.com/mattermost/mattermost-server (Go): affected from 11.5.0; fixed in 11.5.4\n- github.com/mattermost/mattermost-server (Go): affected from 11.5.0; fixed in 11.5.4\n- github.com/mattermost/mattermost-server (Go): affected from 11.6.0; fixed in 11.6.1\n- github.com/mattermost/mattermost-server (Go): affected from 11.6.0; fixed in 11.6.1\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-3473/ (Markdown: https://insights.sbomify.com/CVE-2026-3473/index.md)","id":"CVE-2026-3473","markdown":"https://insights.sbomify.com/CVE-2026-3473/index.md","name":"CVE-2026-3473","record":{"aliases":["GHSA-7pf2-9c95-w332","GO-2026-5817"],"analysis":{"component_type":"web_application","fix_type":"upgrade","impacts":["data_read"],"network_reachable":"yes","non_default_config":false,"product_category":"Mattermost collaboration platform","requires_auth":"low_privilege","summary":"Authenticated users can access and download files belonging to other users or teams via crafted Boards API requests due to improper ownership validation.","user_interaction":"not_required","vuln_class":"missing_authorization"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"Mattermost","cpe":[{"product":"mattermost_server","vendor":"mattermost"}],"cvss":{"score":5.9,"severity":"medium","source":"cna","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N","version":"3.1"},"cwes":[{"id":"CWE-639","name":"Authorization Bypass Through User-Controlled Key"}],"description":"Mattermost versions 11.6.x \u003c= 11.6.0, 11.5.x \u003c= 11.5.3, 11.4.x \u003c= 11.4.4, 10.11.x \u003c= 10.11.14 fail to validate file ownership and access control, which allows an authenticated user to access and download files belonging to other users or teams via crafted Boards API requests using valid file IDs.. Mattermost Advisory ID: MMSA-2026-00620","ecosystems":["Go"],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":true,"headline":"Improper file ownership validation in the Boards API allows unauthorised file access","id":"CVE-2026-3473","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"Go","product":"mattermost:mattermost_server","products":["mattermost:mattermost_server"],"type":"missing_authorization","year":"2026"},"n_packages":9,"n_references":1,"next":{"headline":"EmailKit \u003c= 1.6.3 - Authenticated (Administrator+) Path Traversal via 'emailkit-editor-template' REST API Parameter","id":"CVE-2026-3474"},"packages":[{"ecosystem":"Go","fixed":["10.11.15"],"introduced":["10.11.0"],"last_affected":[],"package":"github.com/mattermost/mattermost-server","purl":null,"source":"GHSA-7pf2-9c95-w332"},{"ecosystem":"Go","fixed":["10.11.15"],"introduced":["10.11.0"],"last_affected":[],"package":"github.com/mattermost/mattermost-server","purl":"pkg:golang/github.com/mattermost/mattermost-server","source":"GHSA-7pf2-9c95-w332"},{"ecosystem":"Go","fixed":["10.11.15+incompatible","11.4.5+incompatible","11.5.4+incompatible","11.6.1+incompatible"],"introduced":["10.11.0+incompatible","11.4.0+incompatible","11.5.0+incompatible","11.6.0+incompatible"],"last_affected":[],"package":"github.com/mattermost/mattermost-server","purl":"pkg:golang/github.com/mattermost/mattermost-server","source":"GO-2026-5817"},{"ecosystem":"Go","fixed":["11.4.5"],"introduced":["11.4.0"],"last_affected":[],"package":"github.com/mattermost/mattermost-server","purl":null,"source":"GHSA-7pf2-9c95-w332"},{"ecosystem":"Go","fixed":["11.4.5"],"introduced":["11.4.0"],"last_affected":[],"package":"github.com/mattermost/mattermost-server","purl":"pkg:golang/github.com/mattermost/mattermost-server","source":"GHSA-7pf2-9c95-w332"},{"ecosystem":"Go","fixed":["11.5.4"],"introduced":["11.5.0"],"last_affected":[],"package":"github.com/mattermost/mattermost-server","purl":null,"source":"GHSA-7pf2-9c95-w332"},{"ecosystem":"Go","fixed":["11.5.4"],"introduced":["11.5.0"],"last_affected":[],"package":"github.com/mattermost/mattermost-server","purl":"pkg:golang/github.com/mattermost/mattermost-server","source":"GHSA-7pf2-9c95-w332"},{"ecosystem":"Go","fixed":["11.6.1"],"introduced":["11.6.0"],"last_affected":[],"package":"github.com/mattermost/mattermost-server","purl":null,"source":"GHSA-7pf2-9c95-w332"},{"ecosystem":"Go","fixed":["11.6.1"],"introduced":["11.6.0"],"last_affected":[],"package":"github.com/mattermost/mattermost-server","purl":"pkg:golang/github.com/mattermost/mattermost-server","source":"GHSA-7pf2-9c95-w332"}],"prev":{"headline":"Markdown image rendering bypass in AI bot tool result posts in Mattermost","id":"CVE-2026-3472"},"products":["Mattermost"],"published":"2026-05-22","related":[{"cvss_score":9.9,"headline":"Account takeover on OAuth/OpenID-enabled servers","id":"CVE-2025-12419","kev_date_added":null,"published":"2025-11-27"},{"cvss_score":9.9,"headline":"Account Takeover via Code Exchange Endpoint","id":"CVE-2025-12421","kev_date_added":null,"published":"2025-11-27"},{"cvss_score":9.9,"headline":"Path Traversal Leading to RCE by Any Authenticated Mattermost User","id":"CVE-2025-4981","kev_date_added":null,"published":"2025-06-20"},{"cvss_score":9.9,"headline":"Arbitrary file read via block duplication in Mattermost Boards","id":"CVE-2025-20051","kev_date_added":null,"published":"2025-02-24"},{"cvss_score":9.9,"headline":"Arbitrary file read in Mattermost Boards via import \u0026 export board archive","id":"CVE-2025-25279","kev_date_added":null,"published":"2025-02-24"},{"cvss_score":9.8,"headline":"Mattermost Server: Insufficient Password-Reset Link Invalidation","id":"CVE-2016-11074","kev_date_added":null,"published":"2020-06-19"},{"cvss_score":9.8,"headline":"Mattermost Server allows attackers to gain privileges by accessing unintended API endpoints with users' credentials","id":"CVE-2017-18885","kev_date_added":null,"published":"2020-06-19"}],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"CC BY 4.0","name":"GitHub Advisory Database","prefix":"GHSA"},{"class":"attribution","licence":"CC BY 4.0","name":"Go Vulnerability Database","prefix":"GO"},{"class":"attribution","licence":"US public information, NVD API terms","name":"NVD"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":"no","exploitation":"none","technical_impact":"partial"},"state":"PUBLISHED","updated":"2026-05-22","vendors":["Mattermost"]},"summary":"Authenticated users can access and download files belonging to other users or teams via crafted Boards API requests due to improper ownership validation.","url":"https://insights.sbomify.com/CVE-2026-3473/"}