{"answers":{"affected":"14 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-2026-3637 in the wild and no public exploit code.","fix":"Upgrade github.com/mattermost/mattermost/server/v8 to a fixed version for your release line: 8.0.0-20260316171743-090408f09f53, 10.11.14, 11.4.4 or 11.5.2.","what":"CVE-2026-3637 is a medium-severity missing authorization vulnerability in Mattermost Mattermost Server, published on 18 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-2026-3637 and fix it if it is affected.\n\nWhat it is: CVE-2026-3637 is a medium-severity missing authorization vulnerability in Mattermost Mattermost Server, published on 18 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-2026-3637 in the wild and no public exploit code.\n\nAffected packages and fixed versions:\n- github.com/mattermost/mattermost/server/v8 (Go): affected all versions; fixed in 8.0.0-20260316171743-090408f09f53\n- github.com/mattermost/mattermost/server/v8 (Go): affected all versions; fixed in 8.0.0-20260316171743-090408f09f53\n- github.com/mattermost/mattermost/server/v8 (Go): affected all versions; fixed in 8.0.0-20260316171743-090408f09f53\n- github.com/mattermost/mattermost/server/v8 (Go): affected from 10.11.0; fixed in 10.11.14\n- github.com/mattermost/mattermost/server/v8 (Go): affected from 10.11.0; fixed in 10.11.14\n- github.com/mattermost/mattermost/server/v8 (Go): affected from 11.4.0; fixed in 11.4.4\n- github.com/mattermost/mattermost/server/v8 (Go): affected from 11.4.0; fixed in 11.4.4\n- github.com/mattermost/mattermost/server/v8 (Go): affected from 11.5.0; fixed in 11.5.2\n- github.com/mattermost/mattermost/server/v8 (Go): affected from 11.5.0; fixed in 11.5.2\n- github.com/mattermost/mattermost-server (Go): affected all versions; fixed in 5.3.2-0.20260316171743-090408f09f53\n- github.com/mattermost/mattermost-server (Go): affected all versions; fixed in 5.3.2-0.20260316171743-090408f09f53\n- github.com/mattermost/mattermost-server (Go): affected from 10.11.0+incompatible; fixed in 10.11.14+incompatible, 11.4.4+incompatible, 11.5.2+incompatible\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-2026-3637/ (Markdown: https://insights.sbomify.com/CVE-2026-3637/index.md)","id":"CVE-2026-3637","markdown":"https://insights.sbomify.com/CVE-2026-3637/index.md","name":"CVE-2026-3637","record":{"aliases":["GHSA-v549-xx3c-6pc8","GO-2026-5651"],"analysis":{"component_type":"web_application","fix_type":"patch","impacts":["data_modify"],"network_reachable":"yes","non_default_config":false,"product_category":"Mattermost chat platform","requires_auth":"low_privilege","summary":"Authenticated attackers with revoked posting privileges can modify existing posts via API requests due to missing 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-862","name":"Missing Authorization"}],"description":"Mattermost versions 11.5.x \u003c= 11.5.1, 10.11.x \u003c= 10.11.13, 11.4.x \u003c= 11.4.3 fail to check the create_post channel permission during post edit operations which allows an authenticated attacker with revoked posting privileges to modify their existing posts via direct API requests to the post update and patch endpoints.. Mattermost Advisory ID: MMSA-2026-00627","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":"Mattermost fails to enforce create_post permission when editing posts","id":"CVE-2026-3637","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"Go","product":"mattermost:mattermost_server","products":["mattermost:mattermost_server"],"type":"missing_authorization","year":"2026"},"n_packages":14,"n_references":1,"next":{"headline":"Missing authorization in Server","id":"CVE-2026-3638"},"packages":[{"ecosystem":"Go","fixed":["5.3.2-0.20260316171743-090408f09f53"],"introduced":["0"],"last_affected":[],"package":"github.com/mattermost/mattermost-server","purl":null,"source":"GHSA-v549-xx3c-6pc8"},{"ecosystem":"Go","fixed":["5.3.2-0.20260316171743-090408f09f53"],"introduced":["0"],"last_affected":[],"package":"github.com/mattermost/mattermost-server","purl":"pkg:golang/github.com/mattermost/mattermost-server","source":"GHSA-v549-xx3c-6pc8"},{"ecosystem":"Go","fixed":["10.11.14+incompatible","11.4.4+incompatible","11.5.2+incompatible"],"introduced":["10.11.0+incompatible","11.4.0+incompatible","11.5.0+incompatible"],"last_affected":[],"package":"github.com/mattermost/mattermost-server","purl":"pkg:golang/github.com/mattermost/mattermost-server","source":"GO-2026-5651"},{"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-2026-5651"},{"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-2026-5651"},{"ecosystem":"Go","fixed":["8.0.0-20260316171743-090408f09f53"],"introduced":["0"],"last_affected":[],"package":"github.com/mattermost/mattermost/server/v8","purl":null,"source":"GHSA-v549-xx3c-6pc8"},{"ecosystem":"Go","fixed":["8.0.0-20260316171743-090408f09f53"],"introduced":["0"],"last_affected":[],"package":"github.com/mattermost/mattermost/server/v8","purl":"pkg:golang/github.com/mattermost/mattermost/server/v8","source":"GHSA-v549-xx3c-6pc8"},{"ecosystem":"Go","fixed":["8.0.0-20260316171743-090408f09f53"],"introduced":["0"],"last_affected":[],"package":"github.com/mattermost/mattermost/server/v8","purl":"pkg:golang/github.com/mattermost/mattermost/server/v8","source":"GO-2026-5651"},{"ecosystem":"Go","fixed":["10.11.14"],"introduced":["10.11.0"],"last_affected":[],"package":"github.com/mattermost/mattermost/server/v8","purl":null,"source":"GHSA-v549-xx3c-6pc8"},{"ecosystem":"Go","fixed":["10.11.14"],"introduced":["10.11.0"],"last_affected":[],"package":"github.com/mattermost/mattermost/server/v8","purl":"pkg:golang/github.com/mattermost/mattermost/server/v8","source":"GHSA-v549-xx3c-6pc8"},{"ecosystem":"Go","fixed":["11.4.4"],"introduced":["11.4.0"],"last_affected":[],"package":"github.com/mattermost/mattermost/server/v8","purl":null,"source":"GHSA-v549-xx3c-6pc8"},{"ecosystem":"Go","fixed":["11.4.4"],"introduced":["11.4.0"],"last_affected":[],"package":"github.com/mattermost/mattermost/server/v8","purl":"pkg:golang/github.com/mattermost/mattermost/server/v8","source":"GHSA-v549-xx3c-6pc8"},{"ecosystem":"Go","fixed":["11.5.2"],"introduced":["11.5.0"],"last_affected":[],"package":"github.com/mattermost/mattermost/server/v8","purl":null,"source":"GHSA-v549-xx3c-6pc8"},{"ecosystem":"Go","fixed":["11.5.2"],"introduced":["11.5.0"],"last_affected":[],"package":"github.com/mattermost/mattermost/server/v8","purl":"pkg:golang/github.com/mattermost/mattermost/server/v8","source":"GHSA-v549-xx3c-6pc8"}],"prev":{"headline":"Sanitize team member data returned by API","id":"CVE-2026-3636"},"products":["Mattermost"],"published":"2026-05-18","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":"2026-05-18","vendors":["Mattermost"]},"summary":"Authenticated attackers with revoked posting privileges can modify existing posts via API requests due to missing permission checks.","url":"https://insights.sbomify.com/CVE-2026-3637/"}