{"id":"CVE-2026-105241","aliases":["DEBIAN-CVE-2026-105241","EUVD-2026-93866","GHSA-r5vq-477m-wcfc","UBUNTU-CVE-2026-105241"],"status":"published","title":"Apache log4net: Unencodable content discards a whole SmtpPickupDirAppender batch","description":"Improper Handling of Unicode Encoding vulnerability in the SmtpPickupDirAppender of Apache log4net.\n\nContent that the mail file writer cannot encode, such as an unpaired UTF-16 surrogate, made the write throw. Every buffered event in the batch was discarded, not only the one carrying the content, and a truncated mail could be left in the pickup directory. A party whose data reaches a log message could suppress the records of other events. Only applications that use SmtpPickupDirAppender are affected.\n\nThis issue affects Apache log4net: from 1.2.9 before 3.5.0.\n\nUsers are recommended to upgrade to version 3.5.0, which fixes the issue.","severity":{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00824,"percentile":0.57859,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-176"],"published":"2026-10-06T19:49:03Z","modified":"2026-10-28T02:31:10Z","affected":[{"source":"osv","ecosystem":"Debian:13","package":"log4net","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.2.10+dfsg-10","1.2.10+dfsg-9"]},{"source":"osv","ecosystem":"Debian:14","package":"log4net","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.2.10+dfsg-10","1.2.10+dfsg-9"]},{"source":"osv","ecosystem":"Ubuntu:16.04:LTS","package":"log4net","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.2.10+dfsg-6","1.2.10+dfsg-7","1.2.10+dfsg-7ubuntu0.16.04.1"]},{"source":"osv","ecosystem":"Ubuntu:18.04:LTS","package":"log4net","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.2.10+dfsg-7","1.2.10+dfsg-7ubuntu0.18.04.1"]},{"source":"osv","ecosystem":"Ubuntu:20.04:LTS","package":"log4net","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.2.10+dfsg-7","1.2.10+dfsg-7ubuntu0.20.04.1"]},{"source":"osv","ecosystem":"Ubuntu:22.04:LTS","package":"log4net","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.2.10+dfsg-8"]},{"source":"osv","ecosystem":"Ubuntu:24.04:LTS","package":"log4net","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.2.10+dfsg-8","1.2.10+dfsg-9"]},{"source":"osv","ecosystem":"Ubuntu:26.10","package":"log4net","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.2.10+dfsg-9build1","1.2.10+dfsg-10"]},{"source":"osv","ecosystem":"Ubuntu:26.04:LTS","package":"log4net","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.2.10+dfsg-9","1.2.10+dfsg-9build1"]}],"products":[{"vendor":"apache","product":"log4net"},{"vendor":"apache software foundation","product":"apache log4net"}],"references":[{"url":"https://github.com/apache/logging-log4net/pull/315","tags":["patch","Patch","fix","report"]},{"url":"https://github.com/apache/logging-log4net/commit/4d2e10f0908199604b4326f9df6d0b43b871e333","tags":["patch","Patch","fix"]},{"url":"https://lists.apache.org/thread.html/hg8dgh3oy8bp3dhb8nsygk9kw2o401ws","tags":["vendor-advisory","Mailing List","Vendor Advisory","advisory"]},{"url":"http://www.openwall.com/lists/oss-security/2026/10/07/15","tags":["Mailing List","Third Party Advisory","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-105241","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-r5vq-477m-wcfc"},{"url":"https://nuget.org/packages","tags":["web"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/105xxx/CVE-2026-105241.json","tags":["advisory"]},{"url":"https://gitbox.apache.org/repos/asf/logging-log4net.git","tags":["package"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-105241","tags":["advisory"]},{"url":"https://ubuntu.com/security/CVE-2026-105241","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-105241","tags":["report"]},{"url":"https://lists.apache.org/thread/hg8dgh3oy8bp3dhb8nsygk9kw2o401ws","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-105241","title":"Apache log4net: Unencodable content discards a whole SmtpPickupDirAppender batch","description":"Improper Handling of Unicode Encoding vulnerability in the SmtpPickupDirAppender of Apache log4net.\n\nContent that the mail file writer cannot encode, such as an unpaired UTF-16 surrogate, made the write throw. Every buffered event in the batch was discarded, not only the one carrying the content, and a truncated mail could be left in the pickup directory. A party whose data reaches a log message could suppress the records of other events. Only applications that use SmtpPickupDirAppender are affected.\n\nThis issue affects Apache log4net: from 1.2.9 before 3.5.0.\n\nUsers are recommended to upgrade to version 3.5.0, which fixes the issue.","status":"published","published":"2026-10-06T19:49:03.994Z","modified":"2026-10-07T14:45:58.074Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","level":"medium","assessor":"cna"}],"cwes":["CWE-176"],"updated_at":"2026-11-02T14:19:56.755658Z"}],"euvd":[{"id":"EUVD-2026-93866","description":"Improper Handling of Unicode Encoding vulnerability in the SmtpPickupDirAppender of Apache log4net.\n\nContent that the mail file writer cannot encode, such as an unpaired UTF-16 surrogate, made the write throw. Every buffered event in the batch was discarded, not only the one carrying the content, and a truncated mail could be left in the pickup directory. A party whose data reaches a log message could suppress the records of other events. Only applications that use SmtpPickupDirAppender are affected.\n\nThis issue affects Apache log4net: from 1.2.9 before 3.5.0.\n\nUsers are recommended to upgrade to version 3.5.0, which fixes the issue.","status":"published","published":"2026-10-06T19:49:03Z","modified":"2026-10-07T14:45:58Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","level":"medium"}],"updated_at":"2026-11-02T17:27:35.509652Z"}],"ghsa":[{"id":"GHSA-r5vq-477m-wcfc","title":"Improper Handling of Unicode Encoding vulnerability in the SmtpPickupDirAppender of Apache...","description":"Improper Handling of Unicode Encoding vulnerability in the SmtpPickupDirAppender of Apache log4net.\n\nContent that the mail file writer cannot encode, such as an unpaired UTF-16 surrogate, made the write throw. Every buffered event in the batch was discarded, not only the one carrying the content, and a truncated mail could be left in the pickup directory. A party whose data reaches a log message could suppress the records of other events. Only applications that use SmtpPickupDirAppender are affected.\n\nThis issue affects Apache log4net: from 1.2.9 before 3.5.0.\n\nUsers are recommended to upgrade to version 3.5.0, which fixes the issue.","status":"published","published":"2026-10-06T21:31:59Z","modified":"2026-10-07T09:32:18Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","level":"medium"}],"cwes":["CWE-176"],"updated_at":"2026-11-02T15:12:53.496212Z"}],"nvd":[{"id":"CVE-2026-105241","description":"Improper Handling of Unicode Encoding vulnerability in the SmtpPickupDirAppender of Apache log4net.\n\nContent that the mail file writer cannot encode, such as an unpaired UTF-16 surrogate, made the write throw. Every buffered event in the batch was discarded, not only the one carrying the content, and a truncated mail could be left in the pickup directory. A party whose data reaches a log message could suppress the records of other events. Only applications that use SmtpPickupDirAppender are affected.\n\nThis issue affects Apache log4net: from 1.2.9 before 3.5.0.\n\nUsers are recommended to upgrade to version 3.5.0, which fixes the issue.","status":"published","published":"2026-10-06T20:17:15.907Z","modified":"2026-10-09T15:29:42.56Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","level":"medium","assessor":"secondary"}],"cwes":["CWE-176"],"updated_at":"2026-11-02T14:12:54.809359Z"}],"osv":[{"id":"CVE-2026-105241","title":"Apache log4net: Unencodable content discards a whole SmtpPickupDirAppender batch","description":"Improper Handling of Unicode Encoding vulnerability in the SmtpPickupDirAppender of Apache log4net.\n\nContent that the mail file writer cannot encode, such as an unpaired UTF-16 surrogate, made the write throw. Every buffered event in the batch was discarded, not only the one carrying the content, and a truncated mail could be left in the pickup directory. A party whose data reaches a log message could suppress the records of other events. Only applications that use SmtpPickupDirAppender are affected.\n\nThis issue affects Apache log4net: from 1.2.9 before 3.5.0.\n\nUsers are recommended to upgrade to version 3.5.0, which fixes the issue.","status":"published","published":"2026-10-06T19:49:03.994Z","modified":"2026-10-28T02:31:10.544848621Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","level":"medium"}],"cwes":["CWE-176"],"updated_at":"2026-11-02T15:44:54.583213Z"},{"id":"DEBIAN-CVE-2026-105241","description":"Improper Handling of Unicode Encoding vulnerability in the SmtpPickupDirAppender of Apache log4net.  Content that the mail file writer cannot encode, such as an unpaired UTF-16 surrogate, made the write throw. Every buffered event in the batch was discarded, not only the one carrying the content, and a truncated mail could be left in the pickup directory. A party whose data reaches a log message could suppress the records of other events. Only applications that use SmtpPickupDirAppender are affected.  This issue affects Apache log4net: from 1.2.9 before 3.5.0.  Users are recommended to upgrade to version 3.5.0, which fixes the issue.","status":"published","published":"2026-10-06T20:17:15.907Z","modified":"2026-10-10T09:47:47.66551851Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","level":"medium"}],"updated_at":"2026-11-02T15:45:48.903138Z"},{"id":"UBUNTU-CVE-2026-105241","description":"Improper Handling of Unicode Encoding vulnerability in the SmtpPickupDirAppender of Apache log4net. Content that the mail file writer cannot encode, such as an unpaired UTF-16 surrogate, made the write throw. Every buffered event in the batch was discarded, not only the one carrying the content, and a truncated mail could be left in the pickup directory. A party whose data reaches a log message could suppress the records of other events. Only applications that use SmtpPickupDirAppender are affected. This issue affects Apache log4net: from 1.2.9 before 3.5.0. Users are recommended to upgrade to version 3.5.0, which fixes the issue.","status":"published","published":"2026-10-06T20:17:00Z","modified":"2026-10-17T12:57:59.492831918Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","level":"medium"}],"updated_at":"2026-11-02T16:55:59.130573Z"}]}}