{"schemaVersion":3,"id":"CVE-2023-4421","aliases":["UBUNTU-CVE-2023-4421","DEBIAN-CVE-2023-4421"],"status":"published","duplicateOf":null,"title":null,"description":"The NSS code used for checking PKCS#1 v1.5 was leaking information useful in mounting Bleichenbacher-like attacks. Both the overall correctness of the padding as well as the length of the encrypted message was leaking through timing side-channel. By sending large number of attacker-selected ciphertexts, the attacker would be able to decrypt a previously intercepted PKCS#1 v1.5 ciphertext (for example, to decrypt a TLS session that used RSA key exchange), or forge a signature using the victim's key. The issue was fixed by implementing the implicit rejection algorithm, in which the NSS returns a deterministic random message in case invalid padding is detected, as proposed in the Marvin Attack paper. This vulnerability affects NSS < 3.61.","dates":{"published":"2023-12-12T17:02:08.801Z","modified":"2025-11-04T19:25:18.220Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":6.5,"severity":"medium","version":"3.1","versionLabel":"v3.1","source":"NVD","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","computed":false,"selection":"backend-summary"},"metrics":[{"version":"3.1","versionLabel":"v3.1","source":"OSV · Ubuntu","score":6.5,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","exploitability":7.2,"impact":6,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"OSV · Debian","score":6.5,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","exploitability":7.2,"impact":6,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"NVD","score":6.5,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","exploitability":null,"impact":null,"computed":false}]},"epss":{"probability":0.00762,"percentile":0.54562,"severity":"low","asOf":"2026-10-19T00:00:00.000Z","change":{"pp":0.006000000000000016,"baselineDate":"2026-09-19T00:00:00.000Z","baselineScore":0.00756},"history":[{"date":"2026-09-14T00:00:00.000Z","score":0.00756,"percentile":null},{"date":"2026-09-15T00:00:00.000Z","score":0.00756,"percentile":null},{"date":"2026-09-16T00:00:00.000Z","score":0.00756,"percentile":null},{"date":"2026-09-17T00:00:00.000Z","score":0.00756,"percentile":null},{"date":"2026-09-18T00:00:00.000Z","score":0.00756,"percentile":null},{"date":"2026-09-19T00:00:00.000Z","score":0.00756,"percentile":null},{"date":"2026-09-20T00:00:00.000Z","score":0.00756,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.00756,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.00756,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.00756,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.00756,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.00756,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.00756,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00762,"percentile":0.54562}],"last30":[{"date":"2026-09-19T00:00:00.000Z","score":0.00756,"percentile":null},{"date":"2026-09-20T00:00:00.000Z","score":0.00756,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.00756,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.00756,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.00756,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.00756,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.00756,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.00756,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00762,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00762,"percentile":0.54562}]},"kev":{"state":"not-listed","entries":[],"listedCount":0,"totalCatalogs":3,"catalogs":[{"source":"cisa","label":"CISA","listed":false,"entry":null},{"source":"enisa","label":"ENISA","listed":false,"entry":null},{"source":"circl","label":"CIRCL","listed":false,"entry":null}]},"ransomware":{"state":"none-recorded","sources":[]},"exploits":[],"exploitCount":0,"weaknesses":[{"id":"CWE-203","name":"Observable Discrepancy","description":"The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor.","type":"weakness","status":"Incomplete","abstraction":"Base","likelihoodOfExploit":null,"url":"https://cwe.mitre.org/data/definitions/203.html"}],"affected":[{"vendor":"debian","product":"nss","name":"nss","label":"nss","ecosystem":"Debian","cpePart":null,"purl":"pkg:deb/debian/nss","purlType":"deb","versions":[{"text":"< 2:3.61-1","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 2:3.61-1","eol":null,"hubHref":null},{"vendor":"ubuntu","product":"nss","name":"nss","label":"nss","ecosystem":"Ubuntu","cpePart":null,"purl":"pkg:deb/ubuntu/nss","purlType":"deb","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null},{"text":"< 2:3.98-0ubuntu0.20.04.1","noFixRecorded":false,"fixedIn":null}],"versionsText":"All versions (No fix recorded) | < 2:3.98-0ubuntu0.20.04.1","eol":null,"hubHref":null},{"vendor":"mozilla","product":"nss","name":"nss","label":"nss","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"≥ unspecified, < 3.61","noFixRecorded":false,"fixedIn":null},{"text":"< 3.6.1","noFixRecorded":false,"fixedIn":null}],"versionsText":"≥ unspecified, < 3.61 | < 3.6.1","eol":null,"hubHref":"/vendor/mozilla/nss"}],"affectedCount":3,"eol":{"hasEol":false,"count":0},"references":[{"url":"https://bugzilla.mozilla.org/show_bug.cgi?id=1651411","label":"bugzilla.mozilla.org/show_bug.cgi?id=1651411","hostname":"bugzilla.mozilla.org","tags":["Issue Tracking"]},{"url":"https://www.mozilla.org/security/advisories/mfsa2023-53/","label":"www.mozilla.org/security/advisories/mfsa2023-53/","hostname":"www.mozilla.org","tags":["Issue Tracking","Vendor Advisory"]},{"url":"https://lists.debian.org/debian-lts-announce/2023/10/msg00039.html","label":"lists.debian.org/debian-lts-announce/2023/10/msg00039.html","hostname":"lists.debian.org","tags":[]},{"url":"https://ubuntu.com/security/CVE-2023-4421","label":"ubuntu.com/security/CVE-2023-4421","hostname":"ubuntu.com","tags":["REPORT"]},{"url":"https://access.redhat.com/security/cve/CVE-2023-4421","label":"access.redhat.com/security/cve/CVE-2023-4421","hostname":"access.redhat.com","tags":["REPORT"]},{"url":"https://people.redhat.com/~hkario/marvin/","label":"people.redhat.com/~hkario/marvin/","hostname":"people.redhat.com","tags":["REPORT"]},{"url":"https://www.mozilla.org/en-US/security/advisories/mfsa2023-53/","label":"www.mozilla.org/en-US/security/advisories/mfsa2023-53/","hostname":"www.mozilla.org","tags":["REPORT"]},{"url":"https://ubuntu.com/security/notices/USN-6727-1","label":"ubuntu.com/security/notices/USN-6727-1","hostname":"ubuntu.com","tags":["Advisory"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2023-4421","label":"www.cve.org/CVERecord?id=CVE-2023-4421","hostname":"www.cve.org","tags":["REPORT"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2023-4421","label":"security-tracker.debian.org/tracker/CVE-2023-4421","hostname":"security-tracker.debian.org","tags":["Advisory"]}],"lineage":{"upstream":[],"downstream":["DLA-3634-1","USN-6727-1"],"duplicates":[],"related":["USN-6727-1"]},"timeline":[{"kind":"published","date":"2023-12-12T17:02:08.801Z","label":"Published","detail":"Vulnerability first disclosed.","source":null},{"kind":"modified","date":"2025-11-04T19:25:18.220Z","label":"Last modified","detail":"Vulnerability information updated.","source":null}],"risk":{"score":26,"level":"medium","profile":"Default","thresholds":{"critical":75,"high":50,"medium":25,"low":10}},"meta":{"dataAsOf":"2026-10-19T23:11:30.168Z","stale":false,"partial":false}}