{"api_version":"1","generated_at":"2026-07-23T20:49:09+00:00","cve":"CVE-2021-43827","urls":{"html":"https://cve.report/CVE-2021-43827","api":"https://cve.report/api/cve/CVE-2021-43827.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2021-43827","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-43827"},"summary":{"title":"CVE-2021-43827","description":"discourse-footnote is a library providing footnotes for posts in Discourse. ### Impact When posting an inline footnote wrapped in `<a>` tags (e.g. `<a>^[footnote]</a>`, the resulting rendered HTML would include a nested `<a>`, which is stripped by Nokogiri because it is not valid. This then caused a javascript error on topic pages because we were looking for an `<a>` element inside the footnote reference span and getting its ID, and because it did not exist we got a null reference error in javascript. Users are advised to update to version 0.2. As a workaround editing offending posts from the rails console or the database console for self-hosters, or disabling the plugin in the admin panel can mitigate this issue.","state":"PUBLIC","assigner":"security-advisories@github.com","published_at":"2021-12-14 23:15:00","updated_at":"2021-12-29 20:31:00"},"problem_types":["CWE-755"],"metrics":[],"references":[{"url":"https://github.com/discourse/discourse-footnote/commit/796617e0131277011207541313522cd1946661ab","name":"https://github.com/discourse/discourse-footnote/commit/796617e0131277011207541313522cd1946661ab","refsource":"MISC","tags":[],"title":"SECURITY: Fix malicious footnote causing clientside errors (#27) · discourse/discourse-footnote@796617e · GitHub","mime":"text/html","httpstatus":"200","archivestatus":"404"},{"url":"https://github.com/discourse/discourse-footnote/security/advisories/GHSA-58vr-c56v-qr57","name":"https://github.com/discourse/discourse-footnote/security/advisories/GHSA-58vr-c56v-qr57","refsource":"CONFIRM","tags":[],"title":"Malicious footnote markup may cause client side errors. · Advisory · discourse/discourse-footnote · GitHub","mime":"text/html","httpstatus":"200","archivestatus":"404"},{"url":"https://www.cve.org/CVERecord?id=CVE-2021-43827","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-43827","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[{"cve_year":"2021","cve_id":"43827","vulnerable":"1","versionEndIncluding":"","cpe1":"cpe","cpe2":"2.3","cpe3":"a","cpe4":"discourse","cpe5":"discourse_footnote","cpe6":"*","cpe7":"*","cpe8":"*","cpe9":"*","cpe10":"*","cpe11":"discourse","cpe12":"*","cpe13":"*"}],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"CVE_data_meta":{"ASSIGNER":"security-advisories@github.com","ID":"CVE-2021-43827","STATE":"PUBLIC","TITLE":"Inline footnotes wrapped in <a> tags can cause errors in discourse-footnotes"},"affects":{"vendor":{"vendor_data":[{"product":{"product_data":[{"product_name":"discourse-footnote","version":{"version_data":[{"version_value":"< 0.2"}]}}]},"vendor_name":"discourse"}]}},"data_format":"MITRE","data_type":"CVE","data_version":"4.0","description":{"description_data":[{"lang":"eng","value":"discourse-footnote is a library providing footnotes for posts in Discourse. ### Impact When posting an inline footnote wrapped in `<a>` tags (e.g. `<a>^[footnote]</a>`, the resulting rendered HTML would include a nested `<a>`, which is stripped by Nokogiri because it is not valid. This then caused a javascript error on topic pages because we were looking for an `<a>` element inside the footnote reference span and getting its ID, and because it did not exist we got a null reference error in javascript. Users are advised to update to version 0.2. As a workaround editing offending posts from the rails console or the database console for self-hosters, or disabling the plugin in the admin panel can mitigate this issue."}]},"impact":{"cvss":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"LOW","baseScore":4.3,"baseSeverity":"MEDIUM","confidentialityImpact":"NONE","integrityImpact":"NONE","privilegesRequired":"LOW","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L","version":"3.1"}},"problemtype":{"problemtype_data":[{"description":[{"lang":"eng","value":"CWE-755: Improper Handling of Exceptional Conditions"}]}]},"references":{"reference_data":[{"name":"https://github.com/discourse/discourse-footnote/security/advisories/GHSA-58vr-c56v-qr57","refsource":"CONFIRM","url":"https://github.com/discourse/discourse-footnote/security/advisories/GHSA-58vr-c56v-qr57"},{"name":"https://github.com/discourse/discourse-footnote/commit/796617e0131277011207541313522cd1946661ab","refsource":"MISC","url":"https://github.com/discourse/discourse-footnote/commit/796617e0131277011207541313522cd1946661ab"}]},"source":{"advisory":"GHSA-58vr-c56v-qr57","discovery":"UNKNOWN"}},"nvd":{"publishedDate":"2021-12-14 23:15:00","lastModifiedDate":"2021-12-29 20:31:00","problem_types":["CWE-755"],"metrics":{"baseMetricV3":{"cvssV3":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"LOW","baseScore":4.3,"baseSeverity":"MEDIUM"},"exploitabilityScore":2.8,"impactScore":1.4},"baseMetricV2":{"cvssV2":{"version":"2.0","vectorString":"AV:N/AC:L/Au:S/C:N/I:N/A:P","accessVector":"NETWORK","accessComplexity":"LOW","authentication":"SINGLE","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"PARTIAL","baseScore":4},"severity":"MEDIUM","exploitabilityScore":8,"impactScore":2.9,"acInsufInfo":false,"obtainAllPrivilege":false,"obtainUserPrivilege":false,"obtainOtherPrivilege":false,"userInteractionRequired":false}},"configurations":{"CVE_data_version":"4.0","nodes":[{"operator":"OR","children":[],"cpe_match":[{"vulnerable":true,"cpe23Uri":"cpe:2.3:a:discourse:discourse_footnote:*:*:*:*:*:discourse:*:*","versionEndExcluding":"0.2","cpe_name":[]}]}]}},"legacy_mitre":{"record":{"CveYear":"2021","CveId":"43827","Ordinal":"221353","Title":"CVE-2021-43827","CVE":"CVE-2021-43827","Year":"2021"},"notes":[{"CveYear":"2021","CveId":"43827","Ordinal":"1","NoteData":"** RESERVED ** This candidate has been reserved by an organization or individual that will use it when announcing a new security problem. When the candidate has been publicized, the details for this candidate will be provided.","Type":"Description","Title":null}]}}}