{"id":"CVE-2020-26291","aliases":["GHSA-3329-pjwv-fjpg"],"url":"https://o3.security/vulnerability/CVE-2020-26291","summary":"Hostname spoofing via backslashes in URL","details":"### Impact\nIf using affected versions to determine a URL's hostname, the hostname can be spoofed by using a backslash (`\\`) character followed by an at (`@`) character. If the hostname is used in security decisions, the decision may be incorrect.\n\nDepending on library usage and attacker intent, impacts may include allow/block list bypasses, SSRF attacks, open redirects, or other undesired behavior.\n\nExample URL: `https://expected-example.com\\@observed-example.com`\nEscaped string: `https://expected-example.com\\\\@observed-example.com` (JavaScript strings must escape backslash)\n\nAffected versions incorrectly return `observed-example.com`. Patched versions correctly return `expected-example.com`. Patched versions match the behavior of other parsers which implement the [WHATWG URL specification](https://url.spec.whatwg.org/), including web browsers and [Node's built-in URL class](https://nodejs.org/api/url.html).\n\n### Patches\nVersion 1.19.4 is patched against all known payload variants. Version 1.19.3 has a partial patch but is still vulnerable to a payload variant.\n\n### References\nhttps://github.com/medialize/URI.js/releases/tag/v1.19.4 (complete fix for this bypass)\nhttps://github.com/medialize/URI.js/releases/tag/v1.19.3 (partial fix for this bypass)\n[PR #233](https://github.com/medialize/URI.js/pull/233) (initial fix for backslash handling)\n\n### For more information\nIf you have any questions or comments about this advisory, open an issue in https://github.com/medialize/URI.js\n\n### Reporter credit\n[Alesandro Ortiz](https://AlesandroOrtiz.com)","published":"2020-12-31T00:15:12.327Z","modified":"2026-10-20T10:52:57.056566648Z","cvss":{"score":6.5,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"urijs","fixedVersion":"1.19.4"}],"fix":{"url":"https://github.com/medialize/URI.js/commit/b02bf037c99ac9316b77ff8bfd840e90becf1155","label":"medialize/URI.js@b02bf03"},"references":[{"type":"ADVISORY","url":"https://github.com/medialize/URI.js/releases/tag/v1.19.4"},{"type":"ADVISORY","url":"https://github.com/medialize/URI.js/security/advisories/GHSA-3329-pjwv-fjpg"},{"type":"ADVISORY","url":"https://www.npmjs.com/package/urijs"},{"type":"FIX","url":"https://github.com/medialize/URI.js/commit/b02bf037c99ac9316b77ff8bfd840e90becf1155"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2020-26291"},{"type":"PACKAGE","url":"https://github.com/medialize/URI.js"},{"type":"WEB","url":"https://www.npmjs.com/advisories/1595"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-20T10:52:57.056566648Z"}}