{"answers":{"affected":"3 open source packages ship an affected version, including github.com/mattermost/mattermost-plugin-msteams. It affects 1 product.","exploited":"There is no known exploitation of CVE-2026-21388 in the wild and no public exploit code.","fix":"Upgrade github.com/mattermost/mattermost-plugin-msteams to 1.15.1-0.20260213190728-6fe4d295592e or later.","what":"CVE-2026-21388 is a low-severity denial of service vulnerability in Mattermost Mattermost Server, published on 9 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-21388 and fix it if it is affected.\n\nWhat it is: CVE-2026-21388 is a low-severity denial of service vulnerability in Mattermost Mattermost Server, published on 9 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2026-21388 in the wild and no public exploit code.\n\nAffected packages and fixed versions:\n- github.com/mattermost/mattermost-plugin-msteams (Go): affected all versions; fixed in 1.15.1-0.20260213190728-6fe4d295592e\n- github.com/mattermost/mattermost-plugin-msteams (Go): affected all versions; fixed in 1.15.1-0.20260213190728-6fe4d295592e\n- github.com/mattermost/mattermost-plugin-msteams (Go): affected all versions; fixed in 1.15.1-0.20260213190728-6fe4d295592e\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-2026-21388/ (Markdown: https://insights.sbomify.com/CVE-2026-21388/index.md)","id":"CVE-2026-21388","markdown":"https://insights.sbomify.com/CVE-2026-21388/index.md","name":"CVE-2026-21388","record":{"aliases":["GHSA-x274-8qfc-hrgf","GO-2026-5734"],"analysis":{"component_type":"web_application","fix_type":"upgrade","impacts":["denial_of_service"],"network_reachable":"yes","non_default_config":false,"product_category":"Mattermost plugin","requires_auth":"none","summary":"An authenticated attacker can cause memory exhaustion and denial of service by sending oversized JSON payloads to the Mattermost Teams plugin webhook endpoint.","user_interaction":"not_required","vuln_class":"denial_of_service"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"Mattermost","cpe":[{"product":"mattermost_server","vendor":"mattermost"}],"cvss":{"score":3.7,"severity":"low","source":"cna","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L","version":"3.1"},"cwes":[{"id":"CWE-770","name":"Allocation of Resources Without Limits or Throttling"}],"description":"Mattermost Plugins versions \u003c=2.3.1 fail to limit the request body size on the {{/lifecycle}} webhook endpoint which allows an authenticated attacker to cause memory exhaustion and denial of service via sending an oversized JSON payload. Mattermost Advisory ID: MMSA-2026-00610","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":"Unbounded Request Body Read in MS Teams Plugin {{/lifecycle}} Webhook Endpoint","id":"CVE-2026-21388","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"Go","product":"mattermost:mattermost_server","products":["mattermost:mattermost_server"],"type":"denial_of_service","year":"2026"},"n_packages":3,"n_references":1,"next":{"headline":"Copeland XWEB and XWEB Pro OS Command Injection","id":"CVE-2026-21389"},"packages":[{"ecosystem":"Go","fixed":["1.15.1-0.20260213190728-6fe4d295592e"],"introduced":["0"],"last_affected":[],"package":"github.com/mattermost/mattermost-plugin-msteams","purl":null,"source":"GHSA-x274-8qfc-hrgf"},{"ecosystem":"Go","fixed":["1.15.1-0.20260213190728-6fe4d295592e"],"introduced":["0"],"last_affected":[],"package":"github.com/mattermost/mattermost-plugin-msteams","purl":"pkg:golang/github.com/mattermost/mattermost-plugin-msteams","source":"GHSA-x274-8qfc-hrgf"},{"ecosystem":"Go","fixed":["1.15.1-0.20260213190728-6fe4d295592e"],"introduced":["0"],"last_affected":[],"package":"github.com/mattermost/mattermost-plugin-msteams","purl":"pkg:golang/github.com/mattermost/mattermost-plugin-msteams","source":"GO-2026-5734"}],"prev":{"headline":"Privilege escalation in Intel(R) LLM Library for PyTorch","id":"CVE-2026-21387"},"products":["Mattermost"],"published":"2026-04-09","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":"2026-04-09","vendors":["Mattermost"]},"summary":"An authenticated attacker can cause memory exhaustion and denial of service by sending oversized JSON payloads to the Mattermost Teams plugin webhook endpoint.","url":"https://insights.sbomify.com/CVE-2026-21388/"}