{"id":"GHSA-3329-pjwv-fjpg","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)","aliases":["CVE-2020-26291"],"modified":"2026-07-08T06:00:21.997445441Z","published":"2020-12-30T23:40:48Z","database_specific":{"severity":"MODERATE","github_reviewed":true,"github_reviewed_at":"2020-12-30T23:40:28Z","nvd_published_at":"2020-12-31T00:15:00Z","cwe_ids":["CWE-20"]},"references":[{"type":"WEB","url":"https://github.com/medialize/URI.js/security/advisories/GHSA-3329-pjwv-fjpg"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2020-26291"},{"type":"WEB","url":"https://github.com/medialize/URI.js/commit/b02bf037c99ac9316b77ff8bfd840e90becf1155"},{"type":"PACKAGE","url":"https://github.com/medialize/URI.js"},{"type":"WEB","url":"https://github.com/medialize/URI.js/releases/tag/v1.19.4"},{"type":"WEB","url":"https://www.npmjs.com/advisories/1595"},{"type":"WEB","url":"https://www.npmjs.com/package/urijs"}],"affected":[{"package":{"name":"urijs","ecosystem":"npm","purl":"pkg:npm/urijs"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"1.19.4"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2020/12/GHSA-3329-pjwv-fjpg/GHSA-3329-pjwv-fjpg.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N"}]}