{"answers":{"affected":"It affects 1 product.","exploited":"There is no known exploitation of CVE-2026-18551 in the wild and no public exploit code.","fix":"No fix has been published for CVE-2026-18551 yet. Limit exposure of the affected software until one is available.","what":"CVE-2026-18551 is a medium-severity vulnerability in Mattermost Mattermost Server, published on 16 Oct 2026. An attacker needs administrator access to exploit it, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-18551 and fix it if it is affected.\n\nWhat it is: CVE-2026-18551 is a medium-severity vulnerability in Mattermost Mattermost Server, published on 16 Oct 2026. An attacker needs administrator access to exploit it, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2026-18551 in the wild and no public exploit code.\n\nAffected product: Mattermost Mattermost Server. No package-level version data is available, so check the vendor advisory linked from the reference page.\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-2026-18551/ (Markdown: https://insights.sbomify.com/CVE-2026-18551/index.md)","id":"CVE-2026-18551","markdown":"https://insights.sbomify.com/CVE-2026-18551/index.md","name":"CVE-2026-18551","record":{"aliases":["GHSA-rh7p-pp3q-6cf8"],"analysis":{"component_type":"web_application","fix_type":"patch","impacts":["privilege_escalation"],"network_reachable":"yes","non_default_config":false,"product_category":"Mattermost collaboration platform","requires_auth":"high_privilege","summary":"An authenticated attacker can escalate a guest account to team or channel admin by exploiting insufficient role validation in the member roles API.","user_interaction":"not_required","vuln_class":"privilege_escalation"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"Mattermost","cpe":[{"product":"mattermost_server","vendor":"mattermost"}],"cvss":{"score":6.5,"severity":"medium","source":"cna","vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N","version":"3.1"},"cwes":[{"id":"CWE-863","name":"Incorrect Authorization"}],"description":"Mattermost versions 11.10.x \u003c= 11.10.0, 11.7.x \u003c= 11.7.9, 11.9.x \u003c= 11.9.1, 11.8.x \u003c= 11.8.5 fail to validate the combination of guest and admin scheme roles which allows an authenticated attacker to escalate a guest account to team or channel admin via a crafted PUT request to the member roles API endpoint.. Mattermost Advisory ID: MMSA-2026-00752","ecosystems":[],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":null,"headline":"Mattermost guest account privilege escalation via member roles API","id":"CVE-2026-18551","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":"mattermost:mattermost_server","products":["mattermost:mattermost_server"],"type":"privilege_escalation","year":"2026"},"n_packages":0,"n_references":1,"next":{"headline":"IBM Db2 Mirror for i is affected by multiple vulnerabilities","id":"CVE-2026-18554"},"packages":[],"prev":{"headline":"Nokri - Job Board WordPress Theme \u003c= 1.6.6 - Unauthenticated Privilege Escalation via 'token' Parameter","id":"CVE-2026-18550"},"products":["Mattermost"],"published":"2026-10-16","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":"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":"total"},"state":"PUBLISHED","updated":"2026-10-20","vendors":["Mattermost"]},"summary":"An authenticated attacker can escalate a guest account to team or channel admin by exploiting insufficient role validation in the member roles API.","url":"https://insights.sbomify.com/CVE-2026-18551/"}