{"schemaVersion":3,"id":"CVE-2026-63576","aliases":[],"status":"published","duplicateOf":null,"title":null,"description":"Improper certificate validation in PkixNameConstraintValidator (ExtractHostFromURL) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a name-constrained subordinate CA, or anyone able to obtain certificates with chosen subjectAltName URIs from such a CA, to bypass permitted or excluded uniformResourceIdentifier name constraints during certification path validation via a URI whose path, query, fragment or userinfo contains characters such as '@' or ':', because the host was extracted by string slicing without first isolating the RFC 3986 authority component, so the host compared against the constraints could differ from the URI's actual host.","dates":{"published":"2026-10-02T07:07:02.513Z","modified":"2026-10-06T19:31:40.267Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":8.2,"severity":"high","version":"4.0","versionLabel":"v4.0","source":"CVE.org","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","computed":false,"selection":"backend-summary"},"metrics":[{"version":"4.0","versionLabel":"v4.0","source":"CVE.org","score":8.2,"severity":"high","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","exploitability":null,"impact":null,"computed":false},{"version":"4.0","versionLabel":"v4.0","source":"NVD","score":8.2,"severity":"high","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","exploitability":null,"impact":null,"computed":false}]},"epss":{"probability":0.00218,"percentile":0.11602,"severity":"low","asOf":"2026-10-21T00:00:00.000Z","change":{"pp":null,"baselineDate":null,"baselineScore":null},"history":[{"date":"2026-10-02T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-21T00:00:00.000Z","score":0.00218,"percentile":0.11602}],"last30":[{"date":"2026-10-02T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.00218,"percentile":null},{"date":"2026-10-21T00:00:00.000Z","score":0.00218,"percentile":0.11602}]},"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-295","name":"Improper Certificate Validation","description":"The product does not validate, or incorrectly validates, a certificate.","type":"weakness","status":"Draft","abstraction":"Base","likelihoodOfExploit":null,"url":"https://cwe.mitre.org/data/definitions/295.html"}],"affected":[{"vendor":"legion of the bouncy castle inc.","product":"bc-csharp","name":"bc-csharp","label":"bc-csharp","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"< 2.7.0","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 2.7.0","eol":null,"hubHref":"/vendor/legion_of_the_bouncy_castle_inc/bc-csharp"}],"affectedCount":1,"eol":{"hasEol":false,"count":0},"references":[{"url":"https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63576","label":"github.com/bcgit/bc-csharp/wiki/CVE-2026-63576","hostname":"github.com","tags":["Vendor Advisory"]},{"url":"https://github.com/bcgit/bc-csharp/commit/f196a22bbf7765cc19b0c4f4645c74ea7ad35e09","label":"github.com/bcgit/bc-csharp/commit/f196a22bbf7765cc19b0c4f4645c74ea7ad35e09","hostname":"github.com","tags":["Patch"]}],"lineage":{"upstream":[],"downstream":[],"duplicates":[],"related":[]},"timeline":[{"kind":"published","date":"2026-10-02T07:07:02.513Z","label":"Published","detail":"Vulnerability first disclosed.","source":null},{"kind":"modified","date":"2026-10-06T19:31:40.267Z","label":"Last modified","detail":"Vulnerability information updated.","source":null}],"risk":{"score":33,"level":"medium","profile":"Default","thresholds":{"critical":75,"high":50,"medium":25,"low":10}},"meta":{"dataAsOf":"2026-10-22T08:22:57.156Z","stale":false,"partial":false}}