{"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-2021-21333 in the wild and no public exploit code.","fix":"Upgrade matrix-synapse to 1.27.0 or later.","what":"CVE-2021-21333 is a medium-severity cross-site scripting vulnerability in Fedoraproject Fedora, published on 26 Mar 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link."},"fix_prompt":"Check this codebase for CVE-2021-21333 and fix it if it is affected.\n\nWhat it is: CVE-2021-21333 is a medium-severity cross-site scripting vulnerability in Fedoraproject Fedora, published on 26 Mar 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.\nExploitation: There is no known exploitation of CVE-2021-21333 in the wild and no public exploit code.\n\nAffected packages and fixed versions:\n- matrix-synapse (PyPI): affected all versions; fixed in 1.27.0\n- matrix-synapse (PyPI): affected all versions; fixed in 1.27.0\n- matrix-synapse (PyPI): affected all versions; fixed in 1.27.0\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-2021-21333/ (Markdown: https://insights.sbomify.com/CVE-2021-21333/index.md)","id":"CVE-2021-21333","markdown":"https://insights.sbomify.com/CVE-2021-21333/index.md","name":"CVE-2021-21333","record":{"aliases":["GHSA-c5f8-35qr-q4fm","PYSEC-2021-134","UBUNTU-CVE-2021-21333"],"analysis":{"component_type":"server_software","fix_type":"upgrade","impacts":["data_modify","security_bypass"],"network_reachable":"yes","non_default_config":false,"product_category":"Matrix homeserver","requires_auth":"none","summary":"Attackers can inject HTML into Synapse notification emails, potentially forging content or bypassing security controls in missed message notifications.","user_interaction":"required","vuln_class":"xss"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"GitHub_M","cpe":[{"product":"fedora","vendor":"fedoraproject"},{"product":"synapse","vendor":"matrix"}],"cvss":{"score":6.1,"severity":"medium","source":"cna","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:H/A:N","version":"3.1"},"cwes":[{"id":"CWE-79","name":"Improper Neutralization of Input During Web Page Generation"},{"id":"CWE-74","name":"Improper Neutralization of Special Elements in Output Used by a Downstream Component"}],"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 1.27.0, the notification emails sent for notifications for missed messages or for an expiring account are subject to HTML injection. In the case of the notification for missed messages, this could allow an attacker to insert forged content into the email. The account expiry feature is not enabled by default and the HTML injection is not controllable by an attacker. This is fixed in version 1.27.0.","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":"HTML injection in email and account expiry notifications","id":"CVE-2021-21333","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"PyPI","product":"fedoraproject:fedora","products":["fedoraproject:fedora"],"type":"xss","year":"2021"},"n_packages":3,"n_references":5,"next":{"headline":"environment variable leak","id":"CVE-2021-21334"},"packages":[{"ecosystem":"PyPI","fixed":["1.27.0"],"introduced":["0"],"last_affected":[],"package":"matrix-synapse","purl":null,"source":"GHSA-c5f8-35qr-q4fm"},{"ecosystem":"PyPI","fixed":["1.27.0"],"introduced":["0"],"last_affected":[],"package":"matrix-synapse","purl":"pkg:pypi/matrix-synapse","source":"GHSA-c5f8-35qr-q4fm"},{"ecosystem":"PyPI","fixed":["1.27.0"],"introduced":["0"],"last_affected":[],"package":"matrix-synapse","purl":"pkg:pypi/matrix-synapse","source":"PYSEC-2021-134"}],"prev":{"headline":"Cross-site scripting (XSS) vulnerability in the password reset endpoint","id":"CVE-2021-21332"},"products":["synapse"],"published":"2021-03-26","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 inject HTML into Synapse notification emails, potentially forging content or bypassing security controls in missed message notifications.","url":"https://insights.sbomify.com/CVE-2021-21333/"}