{"id":"CVE-2021-43523","aliases":["AZL-6928","DEBIAN-CVE-2021-43523","EUVD-2021-30452","GHSA-65xv-vmv6-8r3f"],"status":"published","title":"In uClibc and uClibc-ng before 1.0.39, incorrect handling of special characters in domain names...","description":"In uClibc and uClibc-ng before 1.0.39, incorrect handling of special characters in domain names returned by DNS servers via gethostbyname, getaddrinfo, gethostbyaddr, and getnameinfo can lead to output of wrong hostnames (leading to domain hijacking) or injection into applications (leading to remote code execution, XSS, applications crashes, etc.). In other words, a validation step, which is expected in any stub resolver, does not occur.","severity":{"version":"3.1","score":9.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H","level":"critical","assessor":"primary","from":"nvd"},"epss":{"day":"2026-11-10","score":0.03073,"percentile":0.87763,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-79"],"published":"2021-11-10T14:03:56Z","modified":"2026-10-23T18:04:16Z","fixes":[{"ecosystem":"Azure Linux:2","package":"uclibc-ng","fixed_in":["1.0.37-2"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"Azure Linux:2","package":"uclibc-ng","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.0.37-2"}]}]},{"source":"osv","ecosystem":"Debian:12","package":"uclibc","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.0.35-1","1.0.54-1"]},{"source":"osv","ecosystem":"Debian:13","package":"uclibc","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.0.35-1","1.0.54-1"]},{"source":"osv","ecosystem":"Debian:14","package":"uclibc","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.0.35-1","1.0.54-1"]}],"products":[{"vendor":"uclibc","product":"uclibc"},{"vendor":"uclibc-ng_project","product":"uclibc-ng"}],"references":[{"url":"https://uclibc-ng.org/","tags":["x_refsource_MISC","x_transferred","Vendor Advisory","advisory"]},{"url":"https://github.com/wbx-github/uclibc-ng/commit/0f822af0445e5348ce7b7bd8ce1204244f31d174","tags":["x_refsource_MISC","x_transferred","Patch","Third Party Advisory","fix"]},{"url":"https://www.openwall.com/lists/oss-security/2021/11/09/1","tags":["x_refsource_MISC","x_transferred","Exploit","Mailing List","Third Party Advisory","evidence"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-43523","tags":["web"]},{"url":"https://uclibc-ng.org"},{"url":"https://github.com/advisories/GHSA-65xv-vmv6-8r3f"},{"url":"https://security-tracker.debian.org/tracker/CVE-2021-43523","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2021-43523","description":"In uClibc and uClibc-ng before 1.0.39, incorrect handling of special characters in domain names returned by DNS servers via gethostbyname, getaddrinfo, gethostbyaddr, and getnameinfo can lead to output of wrong hostnames (leading to domain hijacking) or injection into applications (leading to remote code execution, XSS, applications crashes, etc.). In other words, a validation step, which is expected in any stub resolver, does not occur.","status":"published","published":"2021-11-10T14:03:56Z","modified":"2025-05-05T16:46:05.077Z","cvss":[{"version":"3.1","score":9.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H","level":"critical","assessor":"adp"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T14:32:56.689433Z"}],"euvd":[{"id":"EUVD-2021-30452","description":"In uClibc and uClibc-ng before 1.0.39, incorrect handling of special characters in domain names returned by DNS servers via gethostbyname, getaddrinfo, gethostbyaddr, and getnameinfo can lead to output of wrong hostnames (leading to domain hijacking) or injection into applications (leading to remote code execution, XSS, applications crashes, etc.). In other words, a validation step, which is expected in any stub resolver, does not occur.","status":"published","published":"2021-11-10T14:03:56Z","modified":"2025-05-05T16:46:05Z","cvss":[{"version":"3.1","score":9.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H","level":"critical"}],"updated_at":"2026-11-02T20:32:56.053822Z"}],"ghsa":[{"id":"GHSA-65xv-vmv6-8r3f","title":"In uClibc and uClibc-ng before 1.0.39, incorrect handling of special characters in domain names...","description":"In uClibc and uClibc-ng before 1.0.39, incorrect handling of special characters in domain names returned by DNS servers via gethostbyname, getaddrinfo, gethostbyaddr, and getnameinfo can lead to output of wrong hostnames (leading to domain hijacking) or injection into applications (leading to remote code execution, XSS, applications crashes, etc.). In other words, a validation step, which is expected in any stub resolver, does not occur.","status":"published","published":"2022-05-24T19:20:19Z","modified":"2025-05-05T18:30:47Z","cvss":[{"version":"3.1","score":9.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H","level":"critical"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T15:02:06.913728Z"}],"nvd":[{"id":"CVE-2021-43523","description":"In uClibc and uClibc-ng before 1.0.39, incorrect handling of special characters in domain names returned by DNS servers via gethostbyname, getaddrinfo, gethostbyaddr, and getnameinfo can lead to output of wrong hostnames (leading to domain hijacking) or injection into applications (leading to remote code execution, XSS, applications crashes, etc.). In other words, a validation step, which is expected in any stub resolver, does not occur.","status":"published","published":"2021-11-10T15:15:12.213Z","modified":"2026-06-17T04:11:04.027Z","cvss":[{"version":"3.1","score":9.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H","level":"critical","assessor":"primary"},{"version":"3.1","score":9.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H","level":"critical","assessor":"secondary"},{"version":"2.0","score":6.8,"vector":"AV:N/AC:M/Au:N/C:P/I:P/A:P","level":"medium","assessor":"primary"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T14:07:00.984108Z"}],"osv":[{"id":"AZL-6928","title":"CVE-2021-43523 affecting package uclibc-ng for versions less than 1.0.37-2","description":"In uClibc and uClibc-ng before 1.0.39, incorrect handling of special characters in domain names returned by DNS servers via gethostbyname, getaddrinfo, gethostbyaddr, and getnameinfo can lead to output of wrong hostnames (leading to domain hijacking) or injection into applications (leading to remote code execution, XSS, applications crashes, etc.). In other words, a validation step, which is expected in any stub resolver, does not occur.","status":"published","published":"2021-11-10T15:15:12Z","modified":"2026-04-21T04:38:33.66825Z","cvss":[{"version":"3.1","score":9.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H","level":"critical"}],"updated_at":"2026-11-02T15:28:08.630357Z"},{"id":"CVE-2021-43523","description":"In uClibc and uClibc-ng before 1.0.39, incorrect handling of special characters in domain names returned by DNS servers via gethostbyname, getaddrinfo, gethostbyaddr, and getnameinfo can lead to output of wrong hostnames (leading to domain hijacking) or injection into applications (leading to remote code execution, XSS, applications crashes, etc.). In other words, a validation step, which is expected in any stub resolver, does not occur.","status":"published","published":"2021-11-10T15:15:12.213Z","modified":"2026-10-20T14:08:54.656983395Z","cvss":[{"version":"3.1","score":9.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H","level":"critical"}],"updated_at":"2026-11-02T15:44:21.877444Z"},{"id":"DEBIAN-CVE-2021-43523","description":"In uClibc and uClibc-ng before 1.0.39, incorrect handling of special characters in domain names returned by DNS servers via gethostbyname, getaddrinfo, gethostbyaddr, and getnameinfo can lead to output of wrong hostnames (leading to domain hijacking) or injection into applications (leading to remote code execution, XSS, applications crashes, etc.). In other words, a validation step, which is expected in any stub resolver, does not occur.","status":"published","published":"2021-11-10T15:15:12.213Z","modified":"2026-10-23T18:04:16.827266806Z","cvss":[{"version":"3.1","score":9.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H","level":"critical"}],"updated_at":"2026-11-02T15:45:35.799676Z"}]}}