{"answers":{"affected":"3 open source packages ship an affected version, including matrix-synapse. It affects 2 products.","exploited":"There is no known exploitation of CVE-2021-21393 in the wild and no public exploit code.","fix":"Upgrade matrix-synapse to 1.28.0 or later.","what":"CVE-2021-21393 is a medium-severity denial of service vulnerability in Fedoraproject Fedora, published on 12 Apr 2021. Any signed-in user can exploit it over the network, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2021-21393 and fix it if it is affected.\n\nWhat it is: CVE-2021-21393 is a medium-severity denial of service vulnerability in Fedoraproject Fedora, published on 12 Apr 2021. Any signed-in user can exploit it over the network, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2021-21393 in the wild and no public exploit code.\n\nAffected packages and fixed versions:\n- matrix-synapse (PyPI): affected all versions; fixed in 1.28.0\n- matrix-synapse (PyPI): affected all versions; fixed in 1.28.0\n- matrix-synapse (PyPI): affected all versions; fixed in 1.28.0\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-2021-21393/ (Markdown: https://insights.sbomify.com/CVE-2021-21393/index.md)","id":"CVE-2021-21393","markdown":"https://insights.sbomify.com/CVE-2021-21393/index.md","name":"CVE-2021-21393","record":{"aliases":["GHSA-jrh7-mhhx-6h88","PYSEC-2021-26","UBUNTU-CVE-2021-21393"],"analysis":{"component_type":"server_software","fix_type":"upgrade","impacts":["denial_of_service"],"network_reachable":"yes","non_default_config":true,"product_category":"Matrix homeserver","requires_auth":"low_privilege","summary":"Attackers can cause resource exhaustion via improper input validation on groups endpoints, requiring the groups feature to be enabled.","user_interaction":"not_required","vuln_class":"denial_of_service"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"GitHub_M","cpe":[{"product":"fedora","vendor":"fedoraproject"},{"product":"synapse","vendor":"matrix"}],"cvss":{"score":5.3,"severity":"medium","source":"cna","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H","version":"3.1"},"cwes":[{"id":"CWE-20","name":"Improper Input Validation"}],"description":"Synapse is a Matrix reference homeserver written in python (pypi package matrix-synapse). Matrix is an ecosystem for open federated Instant Messaging and VoIP. In Synapse before version 1.28.0 Synapse is missing input validation of some parameters on the endpoints used to confirm third-party identifiers could cause excessive use of disk space and memory leading to resource exhaustion. Note that the groups feature is not part of the Matrix specification and the chosen maximum lengths are arbitrary. Not all clients might abide by them. Refer to referenced GitHub security advisory for additional details including workarounds.","ecosystems":["PyPI"],"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":"Denial of service (via resource exhaustion) due to improper input validation on groups/communities endpoints","id":"CVE-2021-21393","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"PyPI","product":"fedoraproject:fedora","products":["fedoraproject:fedora"],"type":"denial_of_service","year":"2021"},"n_packages":3,"n_references":5,"next":{"headline":"Denial of service (via resource exhaustion) due to improper input validation on third-party identifier endpoints","id":"CVE-2021-21394"},"packages":[{"ecosystem":"PyPI","fixed":["1.28.0"],"introduced":["0"],"last_affected":[],"package":"matrix-synapse","purl":null,"source":"GHSA-jrh7-mhhx-6h88"},{"ecosystem":"PyPI","fixed":["1.28.0"],"introduced":["0"],"last_affected":[],"package":"matrix-synapse","purl":"pkg:pypi/matrix-synapse","source":"GHSA-jrh7-mhhx-6h88"},{"ecosystem":"PyPI","fixed":["1.28.0"],"introduced":["0"],"last_affected":[],"package":"matrix-synapse","purl":"pkg:pypi/matrix-synapse","source":"PYSEC-2021-26"}],"prev":{"headline":"Open redirect via transitional IPv6 addresses on dual-stack networks","id":"CVE-2021-21392"},"products":["synapse"],"published":"2021-04-12","related":[{"cvss_score":9.8,"headline":"PHP-CGI OS Command Injection","id":"CVE-2024-4577","kev_date_added":"2024-06-12","published":"2024-06-09"},{"cvss_score":9.8,"headline":"Grafana Authentication Bypass","id":"CVE-2021-39226","kev_date_added":"2022-08-25","published":"2021-10-05"},{"cvss_score":9.8,"headline":"VMware ESXi and Horizon DaaS OpenSLP Heap-Based Buffer Overflow","id":"CVE-2019-5544","kev_date_added":"2021-11-03","published":"2019-12-06"},{"cvss_score":9.6,"headline":"Google Chromium V8 Type Confusion","id":"CVE-2024-4947","kev_date_added":"2024-05-20","published":"2024-05-15"},{"cvss_score":9.6,"headline":"Google Chromium Visuals Use-After-Free","id":"CVE-2024-4671","kev_date_added":"2024-05-13","published":"2024-05-09"},{"cvss_score":9.6,"headline":"Google Chromium Mojo Insufficient Data Validation","id":"CVE-2022-3075","kev_date_added":"2022-09-08","published":"2022-09-26"},{"cvss_score":9.6,"headline":"Google Chromium Indexed DB API Use-After-Free","id":"CVE-2021-30633","kev_date_added":"2021-11-03","published":"2021-10-08"}],"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":"PyPA Advisory Database","prefix":"PYSEC"},{"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":null,"exploitation":null,"technical_impact":null},"state":"PUBLISHED","updated":"2024-08-03","vendors":["matrix-org"]},"summary":"Attackers can cause resource exhaustion via improper input validation on groups endpoints, requiring the groups feature to be enabled.","url":"https://insights.sbomify.com/CVE-2021-21393/"}