{"answers":{"affected":"6 open source packages ship an affected version, including github.com/mattermost/mattermost/server/v8, github.com/mattermost/mattermost-server and github.com/mattermost/mattermost-server/v5. It affects 1 product.","exploited":"There is no known exploitation of CVE-2026-4055 in the wild and no public exploit code.","fix":"Upgrade github.com/mattermost/mattermost/server/v8 to 8.0.0-20260320113102-f2b3d1c6a945 or later.","what":"CVE-2026-4055 is a medium-severity missing authorization vulnerability in Mattermost Mattermost Server, published on 21 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-2026-4055 and fix it if it is affected.\n\nWhat it is: CVE-2026-4055 is a medium-severity missing authorization vulnerability in Mattermost Mattermost Server, published on 21 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-2026-4055 in the wild and no public exploit code.\n\nAffected packages and fixed versions:\n- github.com/mattermost/mattermost/server/v8 (Go): affected from 8.0.0-20260304132957-9f2616376582; fixed in 8.0.0-20260320113102-f2b3d1c6a945\n- github.com/mattermost/mattermost/server/v8 (Go): affected from 8.0.0-20260304132957-9f2616376582; fixed in 8.0.0-20260320113102-f2b3d1c6a945\n- github.com/mattermost/mattermost/server/v8 (Go): affected from 8.0.0-20260304132957-9f2616376582; fixed in 8.0.0-20260320113102-f2b3d1c6a945\n- github.com/mattermost/mattermost-server (Go): affected all versions; no fix listed\n- github.com/mattermost/mattermost-server/v5 (Go): affected all versions; no fix listed\n- github.com/mattermost/mattermost-server/v6 (Go): affected all versions; no fix listed\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-2026-4055/ (Markdown: https://insights.sbomify.com/CVE-2026-4055/index.md)","id":"CVE-2026-4055","markdown":"https://insights.sbomify.com/CVE-2026-4055/index.md","name":"CVE-2026-4055","record":{"aliases":["GHSA-6cfr-wp44-6qmv","GO-2026-5173"],"analysis":{"component_type":"web_application","fix_type":"patch","impacts":["data_modify"],"network_reachable":"yes","non_default_config":false,"product_category":"Mattermost collaboration platform","requires_auth":"low_privilege","summary":"Authenticated users can create playbook runs in unauthorized teams by manipulating team IDs, bypassing permission checks.","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":4.3,"severity":"medium","source":"cna","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N","version":"3.1"},"cwes":[{"id":"CWE-863","name":"Incorrect Authorization"}],"description":"Mattermost versions 11.5.x \u003c= 11.5.1 fail to validate team-level run_create permission against the target team when creating a playbook run which allows an authenticated team member to create runs in teams where they lack permission via specifying a different team ID in the run creation API request. Mattermost Advisory ID: MMSA-2026-00629","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":"Insufficient permission validation on cross-team playbook run creation","id":"CVE-2026-4055","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"Go","product":"mattermost:mattermost_server","products":["mattermost:mattermost_server"],"type":"missing_authorization","year":"2026"},"n_packages":6,"n_references":1,"next":{"headline":"Missing authorization in User Registration \u0026 Membership – Free \u0026 Paid Memberships, Subscriptions, Content Restriction, User Profile, Custom User Registration \u0026 Login Builder","id":"CVE-2026-4056"},"packages":[{"ecosystem":"Go","fixed":[],"introduced":["0"],"last_affected":[],"package":"github.com/mattermost/mattermost-server","purl":"pkg:golang/github.com/mattermost/mattermost-server","source":"GO-2026-5173"},{"ecosystem":"Go","fixed":[],"introduced":["0"],"last_affected":[],"package":"github.com/mattermost/mattermost-server/v5","purl":"pkg:golang/github.com/mattermost/mattermost-server/v5","source":"GO-2026-5173"},{"ecosystem":"Go","fixed":[],"introduced":["0"],"last_affected":[],"package":"github.com/mattermost/mattermost-server/v6","purl":"pkg:golang/github.com/mattermost/mattermost-server/v6","source":"GO-2026-5173"},{"ecosystem":"Go","fixed":["8.0.0-20260320113102-f2b3d1c6a945"],"introduced":["8.0.0-20260304132957-9f2616376582"],"last_affected":[],"package":"github.com/mattermost/mattermost/server/v8","purl":null,"source":"GHSA-6cfr-wp44-6qmv"},{"ecosystem":"Go","fixed":["8.0.0-20260320113102-f2b3d1c6a945"],"introduced":["8.0.0-20260304132957-9f2616376582"],"last_affected":[],"package":"github.com/mattermost/mattermost/server/v8","purl":"pkg:golang/github.com/mattermost/mattermost/server/v8","source":"GHSA-6cfr-wp44-6qmv"},{"ecosystem":"Go","fixed":["8.0.0-20260320113102-f2b3d1c6a945"],"introduced":["8.0.0-20260304132957-9f2616376582"],"last_affected":[],"package":"github.com/mattermost/mattermost/server/v8","purl":"pkg:golang/github.com/mattermost/mattermost/server/v8","source":"GO-2026-5173"}],"prev":{"headline":"Mattermost doesn't validate the response body of proxied images","id":"CVE-2026-4054"},"products":["Mattermost"],"published":"2026-05-21","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":"2026-05-21","vendors":["Mattermost"]},"summary":"Authenticated users can create playbook runs in unauthorized teams by manipulating team IDs, bypassing permission checks.","url":"https://insights.sbomify.com/CVE-2026-4055/"}