{"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-2026-27659 in the wild and no public exploit code.","fix":"Upgrade github.com/mattermost/mattermost/server/v8 to a fixed version for your release line: 10.11.11, 11.2.3, 11.3.2 or 11.4.1.","what":"CVE-2026-27659 is a medium-severity vulnerability in Mattermost Mattermost Server, published on 25 Mar 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link."},"fix_prompt":"Check this codebase for CVE-2026-27659 and fix it if it is affected.\n\nWhat it is: CVE-2026-27659 is a medium-severity vulnerability in Mattermost Mattermost Server, published on 25 Mar 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.\nExploitation: There is no known exploitation of CVE-2026-27659 in the wild and no public exploit code.\n\nAffected packages and fixed versions:\n- github.com/mattermost/mattermost/server/v8 (Go): affected from 10.11.0-rc1; fixed in 10.11.11\n- github.com/mattermost/mattermost/server/v8 (Go): affected from 10.11.0-rc1; fixed in 10.11.11\n- github.com/mattermost/mattermost/server/v8 (Go): affected from 11.2.0-rc1; fixed in 11.2.3\n- github.com/mattermost/mattermost/server/v8 (Go): affected from 11.2.0-rc1; fixed in 11.2.3\n- github.com/mattermost/mattermost/server/v8 (Go): affected from 11.3.0-rc1; fixed in 11.3.2\n- github.com/mattermost/mattermost/server/v8 (Go): affected from 11.3.0-rc1; fixed in 11.3.2\n- github.com/mattermost/mattermost/server/v8 (Go): affected from 11.4.0-rc1; fixed in 11.4.1\n- github.com/mattermost/mattermost/server/v8 (Go): affected from 11.4.0-rc1; fixed in 11.4.1\n- github.com/mattermost/mattermost/server/v8 (Go): affected from 8.0.0-20260105080200-d27a2195068d; no fix listed\n- github.com/mattermost/mattermost/server/v8 (Go): affected from 8.0.0-20260105080200-d27a2195068d; fixed in 10.11.11\n- github.com/mattermost/mattermost/server/v8 (Go): affected from 8.0.0-20260105080200-d27a2195068d; fixed in 10.11.11\n- github.com/mattermost/mattermost-server (Go): affected from 10.11.0-rc1+incompatible; fixed in 10.11.11+incompatible, 11.2.3+incompatible, 11.3.2+incompatible, 11.4.1+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-2026-27659/ (Markdown: https://insights.sbomify.com/CVE-2026-27659/index.md)","id":"CVE-2026-27659","markdown":"https://insights.sbomify.com/CVE-2026-27659/index.md","name":"CVE-2026-27659","record":{"aliases":["GHSA-rmhw-c3xr-m3xx","GO-2026-5629"],"analysis":{"component_type":"web_application","fix_type":"upgrade","impacts":["data_modify"],"network_reachable":"yes","non_default_config":false,"product_category":"Mattermost collaboration platform","requires_auth":"low_privilege","summary":"Attackers can trick admins into modifying access control policy status via CSRF, requiring an upgrade to Mattermost.","user_interaction":"required","vuln_class":"csrf"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"Mattermost","cpe":[{"product":"mattermost_server","vendor":"mattermost"}],"cvss":{"score":4.6,"severity":"medium","source":"cna","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N","version":"3.1"},"cwes":[{"id":"CWE-352","name":"Cross-Site Request Forgery"}],"description":"Mattermost versions 11.2.x \u003c= 11.2.2, 10.11.x \u003c= 10.11.10, 11.4.x \u003c= 11.4.0, 11.3.x \u003c= 11.3.1 fail to properly validate CSRF tokens in the /api/v4/access_control_policies/{policy_id}/activate endpoint, which allows an attacker to trick an admin into changing access control policy active status via a crafted request.. Mattermost Advisory ID: MMSA-2026-00578","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":"CSRF vulnerability in UpdateAccessControlPolicyActiveStatus endpoint","id":"CVE-2026-27659","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"Go","product":"mattermost:mattermost_server","products":["mattermost:mattermost_server"],"type":"csrf","year":"2026"},"n_packages":14,"n_references":1,"next":{"headline":"Gitea draft releases use insufficient permission checks","id":"CVE-2026-27660"},"packages":[{"ecosystem":"Go","fixed":["10.11.11+incompatible","11.2.3+incompatible","11.3.2+incompatible","11.4.1+incompatible"],"introduced":["10.11.0-rc1+incompatible","11.2.0-rc1+incompatible","11.3.0-rc1+incompatible","11.4.0-rc1+incompatible"],"last_affected":[],"package":"github.com/mattermost/mattermost-server","purl":"pkg:golang/github.com/mattermost/mattermost-server","source":"GO-2026-5629"},{"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-2026-5629"},{"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-2026-5629"},{"ecosystem":"Go","fixed":["10.11.11"],"introduced":["10.11.0-rc1"],"last_affected":[],"package":"github.com/mattermost/mattermost/server/v8","purl":null,"source":"GHSA-rmhw-c3xr-m3xx"},{"ecosystem":"Go","fixed":["10.11.11"],"introduced":["10.11.0-rc1"],"last_affected":[],"package":"github.com/mattermost/mattermost/server/v8","purl":"pkg:golang/github.com/mattermost/mattermost/server/v8","source":"GHSA-rmhw-c3xr-m3xx"},{"ecosystem":"Go","fixed":["11.2.3"],"introduced":["11.2.0-rc1"],"last_affected":[],"package":"github.com/mattermost/mattermost/server/v8","purl":null,"source":"GHSA-rmhw-c3xr-m3xx"},{"ecosystem":"Go","fixed":["11.2.3"],"introduced":["11.2.0-rc1"],"last_affected":[],"package":"github.com/mattermost/mattermost/server/v8","purl":"pkg:golang/github.com/mattermost/mattermost/server/v8","source":"GHSA-rmhw-c3xr-m3xx"},{"ecosystem":"Go","fixed":["11.3.2"],"introduced":["11.3.0-rc1"],"last_affected":[],"package":"github.com/mattermost/mattermost/server/v8","purl":null,"source":"GHSA-rmhw-c3xr-m3xx"},{"ecosystem":"Go","fixed":["11.3.2"],"introduced":["11.3.0-rc1"],"last_affected":[],"package":"github.com/mattermost/mattermost/server/v8","purl":"pkg:golang/github.com/mattermost/mattermost/server/v8","source":"GHSA-rmhw-c3xr-m3xx"},{"ecosystem":"Go","fixed":["11.4.1"],"introduced":["11.4.0-rc1"],"last_affected":[],"package":"github.com/mattermost/mattermost/server/v8","purl":null,"source":"GHSA-rmhw-c3xr-m3xx"},{"ecosystem":"Go","fixed":["11.4.1"],"introduced":["11.4.0-rc1"],"last_affected":[],"package":"github.com/mattermost/mattermost/server/v8","purl":"pkg:golang/github.com/mattermost/mattermost/server/v8","source":"GHSA-rmhw-c3xr-m3xx"},{"ecosystem":"Go","fixed":[],"introduced":["8.0.0-20260105080200-d27a2195068d"],"last_affected":[],"package":"github.com/mattermost/mattermost/server/v8","purl":"pkg:golang/github.com/mattermost/mattermost/server/v8","source":"GO-2026-5629"},{"ecosystem":"Go","fixed":["10.11.11"],"introduced":["8.0.0-20260105080200-d27a2195068d"],"last_affected":[],"package":"github.com/mattermost/mattermost/server/v8","purl":null,"source":"GHSA-rmhw-c3xr-m3xx"},{"ecosystem":"Go","fixed":["10.11.11"],"introduced":["8.0.0-20260105080200-d27a2195068d"],"last_affected":[],"package":"github.com/mattermost/mattermost/server/v8","purl":"pkg:golang/github.com/mattermost/mattermost/server/v8","source":"GHSA-rmhw-c3xr-m3xx"}],"prev":{"headline":"Gitea email settings allow changing another user's primary email address","id":"CVE-2026-27657"},"products":["Mattermost"],"published":"2026-03-25","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":"2026-03-25","vendors":["Mattermost"]},"summary":"Attackers can trick admins into modifying access control policy status via CSRF, requiring an upgrade to Mattermost.","url":"https://insights.sbomify.com/CVE-2026-27659/"}