{"answers":{"affected":"3 open source packages ship an affected version, including matrix-synapse. It affects 1 product.","exploited":"There is no known exploitation of CVE-2020-26891 in the wild and no public exploit code.","fix":"Upgrade matrix-synapse to 1.21.0 or later.","what":"CVE-2020-26891 is a medium-severity cross-site scripting vulnerability in n/a, published on 19 Oct 2020. 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-2020-26891 and fix it if it is affected.\n\nWhat it is: CVE-2020-26891 is a medium-severity cross-site scripting vulnerability in n/a, published on 19 Oct 2020. 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-2020-26891 in the wild and no public exploit code.\n\nAffected packages and fixed versions:\n- matrix-synapse (PyPI): affected all versions; fixed in 1.21.0\n- matrix-synapse (PyPI): affected all versions; fixed in 1.21.0\n- matrix-synapse (PyPI): affected all versions; fixed in 1.21.0\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-2020-26891/ (Markdown: https://insights.sbomify.com/CVE-2020-26891/index.md)","id":"CVE-2020-26891","markdown":"https://insights.sbomify.com/CVE-2020-26891/index.md","name":"CVE-2020-26891","record":{"aliases":["GHSA-3x8c-fmpc-5rmq","PYSEC-2020-238","UBUNTU-CVE-2020-26891"],"analysis":{"component_type":"server_software","fix_type":"upgrade","impacts":["code_execution","account_takeover"],"network_reachable":"yes","non_default_config":false,"product_category":"Matrix Synapse server","requires_auth":"none","summary":"Remote attackers can execute XSS on Matrix Synapse via malicious URLs, potentially compromising user accounts on the hosted domain.","user_interaction":"required","vuln_class":"xss"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"mitre","cpe":[{"product":"synapse","vendor":"matrix"}],"cvss":{"score":6.1,"severity":"medium","source":"nvd","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","version":"3.1"},"cwes":[{"id":"CWE-79","name":"Improper Neutralization of Input During Web Page Generation"}],"description":"AuthRestServlet in Matrix Synapse before 1.21.0 is vulnerable to XSS due to unsafe interpolation of the session GET parameter. This allows a remote attacker to execute an XSS attack on the domain Synapse is hosted on, by supplying the victim user with a malicious URL to the /_matrix/client/r0/auth/*/fallback/web or /_matrix/client/unstable/auth/*/fallback/web Synapse endpoints.","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":"Cross-site scripting (XSS) vulnerability in the fallback authentication endpoint","id":"CVE-2020-26891","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"PyPI","product":null,"products":[],"type":"xss","year":"2020"},"n_packages":3,"n_references":4,"next":{"headline":"Incorrect handling of credential expiry by /nats-io/nats-server","id":"CVE-2020-26892"},"packages":[{"ecosystem":"PyPI","fixed":["1.21.0"],"introduced":["0"],"last_affected":[],"package":"matrix-synapse","purl":null,"source":"GHSA-3x8c-fmpc-5rmq"},{"ecosystem":"PyPI","fixed":["1.21.0"],"introduced":["0"],"last_affected":[],"package":"matrix-synapse","purl":"pkg:pypi/matrix-synapse","source":"GHSA-3x8c-fmpc-5rmq"},{"ecosystem":"PyPI","fixed":["1.21.0"],"introduced":["0"],"last_affected":[],"package":"matrix-synapse","purl":"pkg:pypi/matrix-synapse","source":"PYSEC-2020-238"}],"prev":{"headline":"Denial of service attack due to invalid JSON","id":"CVE-2020-26890"},"products":["n/a"],"published":"2020-10-19","related":[{"cvss_score":9.8,"headline":"Improper Verification of Cryptographic Signature in matrix-synapse","id":"CVE-2019-18835","kev_date_added":null,"published":"2019-11-07"},{"cvss_score":8.7,"headline":"Synapse allows a a malformed invite to break the invitee's `/sync`","id":"CVE-2024-52815","kev_date_added":null,"published":"2024-12-03"},{"cvss_score":8.2,"headline":"Synapse allows unsupported content types to lead to memory exhaustion","id":"CVE-2024-52805","kev_date_added":null,"published":"2024-12-03"},{"cvss_score":8.2,"headline":"Synapse can be forced to thumbnail unexpected file formats, invoking external, potentially untrustworthy decoders","id":"CVE-2024-53863","kev_date_added":null,"published":"2024-12-03"},{"cvss_score":7.5,"headline":"Synapse denial of service through media disk space consumption","id":"CVE-2024-37302","kev_date_added":null,"published":"2024-12-03"},{"cvss_score":7.5,"headline":"Matrix Synapse Authorization Error","id":"CVE-2018-12423","kev_date_added":null,"published":"2018-06-14"},{"cvss_score":7.5,"headline":"Matrix Synapse Security Filtering Flaw","id":"CVE-2018-12291","kev_date_added":null,"published":"2018-06-13"}],"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":"2024-08-04","vendors":["n/a"]},"summary":"Remote attackers can execute XSS on Matrix Synapse via malicious URLs, potentially compromising user accounts on the hosted domain.","url":"https://insights.sbomify.com/CVE-2020-26891/"}