{"schemaVersion":3,"id":"CVE-2026-50256","aliases":["UBUNTU-CVE-2026-50256","DEBIAN-CVE-2026-50256"],"status":"published","duplicateOf":null,"title":null,"description":"A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland. A mismatch between the X server and the libXfont2 library's maximum font name length can cause a stack buffer overflow during font alias resolution. The server allocates a 256 byte stack buffer but libXfont2's alias target name length is 1024 bytes. A font alias name between 257 and 1023 bytes causes the X server to copy that name into the undersized stack buffer without further checks. This may be used to crash the server, or for privilege escalation if the X server runs as root.","dates":{"published":"2026-06-05T10:31:22.122Z","modified":"2026-09-28T11:45:55.534Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":7.8,"severity":"high","version":"3.1","versionLabel":"v3.1","source":"CVE.org","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","computed":false,"selection":"backend-summary"},"metrics":[{"version":"3.1","versionLabel":"v3.1","source":"CVE.org","score":7.8,"severity":"high","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","exploitability":null,"impact":null,"computed":false},{"version":"3.1","versionLabel":"v3.1","source":"OSV · Ubuntu","score":7.8,"severity":"high","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","exploitability":4.6,"impact":9.8,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"OSV · Debian","score":7.8,"severity":"high","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","exploitability":4.6,"impact":9.8,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"NVD","score":7.8,"severity":"high","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","exploitability":null,"impact":null,"computed":false}]},"epss":{"probability":0.0021,"percentile":0.10666,"severity":"low","asOf":"2026-10-20T00:00:00.000Z","change":{"pp":0.052999999999999985,"baselineDate":"2026-09-20T00:00:00.000Z","baselineScore":0.00157},"history":[{"date":"2026-09-14T00:00:00.000Z","score":0.00157,"percentile":null},{"date":"2026-09-15T00:00:00.000Z","score":0.00157,"percentile":null},{"date":"2026-09-16T00:00:00.000Z","score":0.00157,"percentile":null},{"date":"2026-09-17T00:00:00.000Z","score":0.00157,"percentile":null},{"date":"2026-09-18T00:00:00.000Z","score":0.00157,"percentile":null},{"date":"2026-09-19T00:00:00.000Z","score":0.00157,"percentile":null},{"date":"2026-09-20T00:00:00.000Z","score":0.00157,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.00157,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.00157,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.00157,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.0021,"percentile":0.10666}],"last30":[{"date":"2026-09-20T00:00:00.000Z","score":0.00157,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.00157,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.00157,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.00157,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.0021,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.0021,"percentile":0.10666}]},"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-121","name":"Stack-based Buffer Overflow","description":"A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).","type":"weakness","status":"Draft","abstraction":"Variant","likelihoodOfExploit":"High","url":"https://cwe.mitre.org/data/definitions/121.html"}],"affected":[{"vendor":"debian","product":"xorg-server","name":"xorg-server","label":"xorg-server","ecosystem":"Debian","cpePart":null,"purl":"pkg:deb/debian/xorg-server","purlType":"deb","versions":[{"text":"< 2:21.1.7-3+deb12u13","noFixRecorded":false,"fixedIn":null},{"text":"< 2:21.1.16-1.3+deb13u3","noFixRecorded":false,"fixedIn":null},{"text":"< 2:21.1.23-1","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 2:21.1.7-3+deb12u13 | < 2:21.1.16-1.3+deb13u3 | < 2:21.1.23-1","eol":null,"hubHref":null},{"vendor":"debian","product":"xwayland","name":"xwayland","label":"xwayland","ecosystem":"Debian","cpePart":null,"purl":"pkg:deb/debian/xwayland","purlType":"deb","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null},{"text":"< 2:24.1.12-1","noFixRecorded":false,"fixedIn":null}],"versionsText":"All versions (No fix recorded) | < 2:24.1.12-1","eol":null,"hubHref":null},{"vendor":"ubuntu","product":"xorg-server","name":"xorg-server","label":"xorg-server","ecosystem":"Ubuntu","cpePart":null,"purl":"pkg:deb/ubuntu/xorg-server","purlType":"deb","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null}],"versionsText":"All versions (No fix recorded)","eol":null,"hubHref":null},{"vendor":"ubuntu","product":"xorg-server-hwe-16.04","name":"xorg-server-hwe-16.04","label":"xorg-server-hwe-16.04","ecosystem":"Ubuntu","cpePart":null,"purl":"pkg:deb/ubuntu/xorg-server-hwe-16.04","purlType":"deb","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null}],"versionsText":"All versions (No fix recorded)","eol":null,"hubHref":null},{"vendor":"ubuntu","product":"xorg-server-hwe-18.04","name":"xorg-server-hwe-18.04","label":"xorg-server-hwe-18.04","ecosystem":"Ubuntu","cpePart":null,"purl":"pkg:deb/ubuntu/xorg-server-hwe-18.04","purlType":"deb","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null}],"versionsText":"All versions (No fix recorded)","eol":null,"hubHref":null},{"vendor":"ubuntu","product":"xwayland","name":"xwayland","label":"xwayland","ecosystem":"Ubuntu","cpePart":null,"purl":"pkg:deb/ubuntu/xwayland","purlType":"deb","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null}],"versionsText":"All versions (No fix recorded)","eol":null,"hubHref":null},{"vendor":"redhat","product":"enterprise_linux","name":"enterprise linux","label":"enterprise_linux","ecosystem":null,"cpePart":"o","purl":null,"purlType":null,"versions":[{"text":"7.0","noFixRecorded":false,"fixedIn":null},{"text":"8.0","noFixRecorded":false,"fixedIn":null},{"text":"9.0","noFixRecorded":false,"fixedIn":null},{"text":"10.0","noFixRecorded":false,"fixedIn":null}],"versionsText":"7.0 | 8.0 | 9.0 | 10.0","eol":{"isEol":true,"eolDate":"2024-06-30T00:00:00.000Z","matchMethod":"cpe","cycle":{"name":"7","label":"7 (ELS)","eolFrom":"2024-06-30T00:00:00.000Z","isLts":true,"isMaintained":true,"latestVersion":"7.9"},"product":{"name":"rhel","label":"Red Hat Enterprise Linux","category":"os"}},"hubHref":"/vendor/redhat/enterprise_linux"},{"vendor":"x.org","product":"x_server","name":"x server","label":"x_server","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"< 21.1.23","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 21.1.23","eol":null,"hubHref":"/vendor/xorg/x_server"},{"vendor":"x.org","product":"xwayland","name":"xwayland","label":"xwayland","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"< 24.1.12","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 24.1.12","eol":null,"hubHref":"/vendor/xorg/xwayland"}],"affectedCount":9,"eol":{"hasEol":true,"count":1},"references":[{"url":"https://access.redhat.com/errata/RHSA-2026:26562","label":"access.redhat.com/errata/RHSA-2026:26562","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:26566","label":"access.redhat.com/errata/RHSA-2026:26566","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:26590","label":"access.redhat.com/errata/RHSA-2026:26590","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:26610","label":"access.redhat.com/errata/RHSA-2026:26610","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:26709","label":"access.redhat.com/errata/RHSA-2026:26709","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:28923","label":"access.redhat.com/errata/RHSA-2026:28923","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:29844","label":"access.redhat.com/errata/RHSA-2026:29844","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:36083","label":"access.redhat.com/errata/RHSA-2026:36083","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:36085","label":"access.redhat.com/errata/RHSA-2026:36085","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:36086","label":"access.redhat.com/errata/RHSA-2026:36086","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:36087","label":"access.redhat.com/errata/RHSA-2026:36087","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:36632","label":"access.redhat.com/errata/RHSA-2026:36632","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:36633","label":"access.redhat.com/errata/RHSA-2026:36633","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:36634","label":"access.redhat.com/errata/RHSA-2026:36634","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:36768","label":"access.redhat.com/errata/RHSA-2026:36768","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:36791","label":"access.redhat.com/errata/RHSA-2026:36791","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:36792","label":"access.redhat.com/errata/RHSA-2026:36792","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:36798","label":"access.redhat.com/errata/RHSA-2026:36798","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:38502","label":"access.redhat.com/errata/RHSA-2026:38502","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:38810","label":"access.redhat.com/errata/RHSA-2026:38810","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:46377","label":"access.redhat.com/errata/RHSA-2026:46377","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:46382","label":"access.redhat.com/errata/RHSA-2026:46382","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:46385","label":"access.redhat.com/errata/RHSA-2026:46385","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:46392","label":"access.redhat.com/errata/RHSA-2026:46392","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:46456","label":"access.redhat.com/errata/RHSA-2026:46456","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:46460","label":"access.redhat.com/errata/RHSA-2026:46460","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:46473","label":"access.redhat.com/errata/RHSA-2026:46473","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2026:49519","label":"access.redhat.com/errata/RHSA-2026:49519","hostname":"access.redhat.com","tags":["Vendor Advisory","X Refsource REDHAT"]},{"url":"https://access.redhat.com/security/cve/CVE-2026-50256","label":"access.redhat.com/security/cve/CVE-2026-50256","hostname":"access.redhat.com","tags":["VDB Entry","X Refsource REDHAT","Vendor Advisory"]},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2485380","label":"bugzilla.redhat.com/show_bug.cgi?id=2485380","hostname":"bugzilla.redhat.com","tags":["Issue Tracking","X Refsource REDHAT","Vendor Advisory"]},{"url":"https://gitlab.freedesktop.org/xorg/xserver/-/commit/bb5158f962dc935e58ef8b4b5fcb31be201a6e07","label":"gitlab.freedesktop.org/xorg/xserver/-/commit/bb5158f962dc935e58ef8b4b5fcb31be201a6e07","hostname":"gitlab.freedesktop.org","tags":["REPORT","Patch"]},{"url":"https://lists.x.org/archives/xorg-announce/2026-June/003702.html","label":"lists.x.org/archives/xorg-announce/2026-June/003702.html","hostname":"lists.x.org","tags":["Mailing List","Third Party Advisory"]},{"url":"https://redhat.atlassian.net/browse/PSIRTSUPT-16950","label":"redhat.atlassian.net/browse/PSIRTSUPT-16950","hostname":"redhat.atlassian.net","tags":["Permissions Required"]},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-50256.json","label":"security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-50256.json","hostname":"security.access.redhat.com","tags":["X Sadp Csaf Vex"]},{"url":"https://ubuntu.com/security/CVE-2026-50256","label":"ubuntu.com/security/CVE-2026-50256","hostname":"ubuntu.com","tags":["REPORT"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-50256","label":"www.cve.org/CVERecord?id=CVE-2026-50256","hostname":"www.cve.org","tags":["REPORT"]},{"url":"https://www.openwall.com/lists/oss-security/2026/06/02/1","label":"www.openwall.com/lists/oss-security/2026/06/02/1","hostname":"www.openwall.com","tags":["REPORT"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-50256","label":"security-tracker.debian.org/tracker/CVE-2026-50256","hostname":"security-tracker.debian.org","tags":["Advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-50256","label":"nvd.nist.gov/vuln/detail/CVE-2026-50256","hostname":"nvd.nist.gov","tags":["Oval","Advisory"]}],"lineage":{"upstream":[],"downstream":["RHSA-2026:26562","RHSA-2026:26566","RHSA-2026:26590","RHSA-2026:26610","RHSA-2026:26709","RHSA-2026:28923","RHSA-2026:29844","RHSA-2026:36083","RHSA-2026:36085","RHSA-2026:36086","RHSA-2026:36087","RHSA-2026:36632","RHSA-2026:36633","RHSA-2026:36634","RHSA-2026:36768","RHSA-2026:36791","RHSA-2026:36792","RHSA-2026:36798","RHSA-2026:38502","RHSA-2026:38810","RHSA-2026:46377","RHSA-2026:46382","RHSA-2026:46385","RHSA-2026:46392","RHSA-2026:46456","RHSA-2026:46460","RHSA-2026:46473","RHSA-2026:49519"],"duplicates":[],"related":[]},"timeline":[{"kind":"published","date":"2026-06-05T10:31:22.122Z","label":"Published","detail":"Vulnerability first disclosed.","source":null},{"kind":"modified","date":"2026-09-28T11:45:55.534Z","label":"Last modified","detail":"Vulnerability information updated.","source":null}],"risk":{"score":31,"level":"medium","profile":"Default","thresholds":{"critical":75,"high":50,"medium":25,"low":10}},"meta":{"dataAsOf":"2026-10-20T17:20:40.321Z","stale":false,"partial":false}}