{"cve":"CVE-2021-26540","nvd":{"published":"2021-02-08T17:15:13.737","modified":"2026-06-17T03:43:27.400","status":"Modified","description":"Apostrophe Technologies sanitize-html before 2.3.2 does not properly validate the hostnames set by the \"allowedIframeHostnames\" option when the \"allowIframeRelativeUrls\" is set to true, which allows attackers to bypass hostname whitelist for iframe element, related using an src value that starts with \"/\\\\example.com\".","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","score":5.3},"cwes":[],"references":["https://advisory.checkmarx.net/advisory/CX-2021-4309","https://github.com/apostrophecms/sanitize-html/blob/main/CHANGELOG.md#232-2021-01-26","https://github.com/apostrophecms/sanitize-html/pull/460","https://advisory.checkmarx.net/advisory/CX-2021-4309","https://github.com/apostrophecms/sanitize-html/blob/main/CHANGELOG.md#232-2021-01-26"],"products":["apostrophecms:sanitize-html"],"source":"nvd","synced_at":"2026-10-19T21:14:10.479542811+00:00"},"epss":{"cve":"CVE-2021-26540","score":0.01754,"percentile":0.7792,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-mjxr-4v3x-q3m4","url":"https://osv.dev/vulnerability/GHSA-mjxr-4v3x-q3m4","summary":"Improper Input Validation in sanitize-html","modified":"2023-11-08T04:05:21.154746Z","packages":[{"ecosystem":"npm","name":"sanitize-html","purl":"pkg:npm/sanitize-html","ranges":["<2.3.2"],"fixed":["2.3.2"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}