{"id":"CVE-2021-23953","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-23953","generatedAt":"2026-10-27T20:22:59.059Z","title":"If a user clicked into a specifically crafted PDF, the PDF reader could be confused into leaking cross-origin information, when said information is served as chunked data.","description":"If a user clicked into a specifically crafted PDF, the PDF reader could be confused into leaking cross-origin information, when said information is served as chunked data. This vulnerability affects Firefox < 85, Thunderbird < 78.7, and Firefox ESR < 78.7.","published":"2021-02-26T03:15:13.000Z","lastModified":"2026-06-17T03:39:04.000Z","status":"Modified","sourceIdentifier":"security@mozilla.org","cvss":{"version":"3.1","score":4.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N"},"cwe":[],"affected":["mozilla/firefox","mozilla/firefox esr","mozilla/thunderbird"],"epss":{"score":0.01056,"percentile":0.6421,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (1.06%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"https://bugzilla.mozilla.org/show_bug.cgi?id=1683940","tags":["Issue Tracking","Permissions Required","Vendor Advisory"],"source":"security@mozilla.org"},{"url":"https://www.mozilla.org/security/advisories/mfsa2021-03/","tags":["Release Notes","Vendor Advisory"],"source":"security@mozilla.org"},{"url":"https://www.mozilla.org/security/advisories/mfsa2021-04/","tags":["Release Notes","Vendor Advisory"],"source":"security@mozilla.org"},{"url":"https://www.mozilla.org/security/advisories/mfsa2021-05/","tags":["Release Notes","Vendor Advisory"],"source":"security@mozilla.org"},{"url":"https://bugzilla.mozilla.org/show_bug.cgi?id=1683940","tags":["Issue Tracking","Permissions Required","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.mozilla.org/security/advisories/mfsa2021-03/","tags":["Release Notes","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.mozilla.org/security/advisories/mfsa2021-04/","tags":["Release Notes","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.mozilla.org/security/advisories/mfsa2021-05/","tags":["Release Notes","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-23953","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}