{"schemaVersion":3,"id":"CVE-2026-105244","aliases":["UBUNTU-CVE-2026-105244","DEBIAN-CVE-2026-105244"],"status":"published","duplicateOf":null,"title":null,"description":"Improper Encoding or Escaping of Output vulnerability in the RemoteSyslogAppender of Apache log4net.\n\nEvery character outside visible ASCII and space was removed from the record instead of being escaped, so non-ASCII text and control characters such as tabs disappeared without notice. A party whose data reaches a log message could make a distinct value look identical in the record, for example a user name holding a zero-width space logged as admin. Only applications that use RemoteSyslogAppender are affected.\n\nThis issue affects Apache log4net: from 1.2.12 before 3.5.0.\n\nUsers are recommended to upgrade to version 3.5.0, which fixes the issue.","dates":{"published":"2026-10-06T19:52:31.116Z","modified":"2026-10-07T14:50:49.648Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":5.3,"severity":"medium","version":"3.1","versionLabel":"v3.1","source":"CVE.org","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","computed":false,"selection":"backend-summary"},"metrics":[{"version":"3.1","versionLabel":"v3.1","source":"CVE.org","score":5.3,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","exploitability":null,"impact":null,"computed":false},{"version":"3.1","versionLabel":"v3.1","source":"OSV · Ubuntu","score":5.3,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","exploitability":10,"impact":2.3,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"OSV · Debian","score":5.3,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","exploitability":10,"impact":2.3,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"NVD","score":5.3,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","exploitability":null,"impact":null,"computed":false}]},"epss":{"probability":0.00823,"percentile":0.56619,"severity":"low","asOf":"2026-10-19T00:00:00.000Z","change":{"pp":null,"baselineDate":null,"baselineScore":null},"history":[{"date":"2026-10-07T00:00:00.000Z","score":0.00338,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00338,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00338,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00823,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00823,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00823,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00823,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00823,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00823,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00823,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00823,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00823,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00823,"percentile":0.56619}],"last30":[{"date":"2026-10-07T00:00:00.000Z","score":0.00338,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00338,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00338,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00823,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00823,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00823,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00823,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00823,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00823,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00823,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00823,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00823,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00823,"percentile":0.56619}]},"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-116","name":"Improper Encoding or Escaping of Output","description":"The product prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. As a result, the intended structure of the message is not preserved.","type":"weakness","status":"Draft","abstraction":"Class","likelihoodOfExploit":"High","url":"https://cwe.mitre.org/data/definitions/116.html"}],"affected":[{"vendor":"apache software foundation","product":"apache log4net","name":"Apache Log4net","label":"apache log4net","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"≥ 1.2.12, < 3.5.0","noFixRecorded":false,"fixedIn":null},{"text":"≥ 56a2e146e21ff4737e1ff3ec308810e667873947, < 77717061b20d4346b6c0ce6b54643d85fb348bc7","noFixRecorded":false,"fixedIn":null}],"versionsText":"≥ 1.2.12, < 3.5.0 | ≥ 56a2e146e21ff4737e1ff3ec308810e667873947, < 77717061b20d4346b6c0ce6b54643d85fb348bc7","eol":null,"hubHref":"/vendor/apache_software_foundation/apache_log4net"},{"vendor":"apache","product":"log4net","name":"log4net","label":"log4net","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"≥ 1.2.12, < 3.5.0","noFixRecorded":false,"fixedIn":null}],"versionsText":"≥ 1.2.12, < 3.5.0","eol":null,"hubHref":"/vendor/apache/log4net"},{"vendor":"debian","product":"log4net","name":"log4net","label":"log4net","ecosystem":"Debian","cpePart":null,"purl":"pkg:deb/debian/log4net","purlType":"deb","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null}],"versionsText":"All versions (No fix recorded)","eol":null,"hubHref":null},{"vendor":"ubuntu","product":"log4net","name":"log4net","label":"log4net","ecosystem":"Ubuntu","cpePart":null,"purl":"pkg:deb/ubuntu/log4net","purlType":"deb","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null}],"versionsText":"All versions (No fix recorded)","eol":null,"hubHref":null}],"affectedCount":4,"eol":{"hasEol":false,"count":0},"references":[{"url":"https://github.com/apache/logging-log4net/pull/315","label":"github.com/apache/logging-log4net/pull/315","hostname":"github.com","tags":["Patch","REPORT","Vendor Advisory"]},{"url":"https://github.com/apache/logging-log4net/commit/77717061b20d4346b6c0ce6b54643d85fb348bc7","label":"github.com/apache/logging-log4net/commit/77717061b20d4346b6c0ce6b54643d85fb348bc7","hostname":"github.com","tags":["Patch"]},{"url":"https://lists.apache.org/thread.html/q7649hhdodthoqw8jsjgtnb4m8qfy6d6","label":"lists.apache.org/thread.html/q7649hhdodthoqw8jsjgtnb4m8qfy6d6","hostname":"lists.apache.org","tags":["Vendor Advisory","Mailing List"]},{"url":"http://www.openwall.com/lists/oss-security/2026/10/07/19","label":"www.openwall.com/lists/oss-security/2026/10/07/19","hostname":"www.openwall.com","tags":["Mailing List","Third Party Advisory"]},{"url":"https://ubuntu.com/security/CVE-2026-105244","label":"ubuntu.com/security/CVE-2026-105244","hostname":"ubuntu.com","tags":["REPORT"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-105244","label":"www.cve.org/CVERecord?id=CVE-2026-105244","hostname":"www.cve.org","tags":["REPORT"]},{"url":"https://lists.apache.org/thread/q7649hhdodthoqw8jsjgtnb4m8qfy6d6","label":"lists.apache.org/thread/q7649hhdodthoqw8jsjgtnb4m8qfy6d6","hostname":"lists.apache.org","tags":["REPORT"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-105244","label":"security-tracker.debian.org/tracker/CVE-2026-105244","hostname":"security-tracker.debian.org","tags":["Advisory"]}],"lineage":{"upstream":[],"downstream":[],"duplicates":[],"related":[]},"timeline":[{"kind":"published","date":"2026-10-06T19:52:31.116Z","label":"Published","detail":"Vulnerability first disclosed.","source":null},{"kind":"modified","date":"2026-10-07T14:50:49.648Z","label":"Last modified","detail":"Vulnerability information updated.","source":null}],"risk":{"score":21,"level":"low","profile":"Default","thresholds":{"critical":75,"high":50,"medium":25,"low":10}},"meta":{"dataAsOf":"2026-10-19T14:47:54.516Z","stale":false,"partial":false}}