{"id":"UBUNTU-CVE-2026-19953","details":"URI versions before 5.36 for Perl encode non-NFC host names to non-standard punycode labels via missing normalization in nameprep. nameprep lowercases each host label but performs no Unicode normalization. IDNA requires a label to be normalized to Form C before it is encoded (RFC 5891), so a label that is not already in NFC is encoded to a different A-label than its normalized form. A label built from the precomposed Devanagari sequence U+0958 U+093E encodes to xn--72b5c without normalization but to xn--11b2fg after NFC normalization, and xn--72b5c does not round-trip back to the original label. Any caller that reads host() from a URI built from untrusted input and uses it for a security decision (an allow or deny list, an SSRF filter, deduplication, a cache key) sees the non-standard label, while a client that fetches the same URL resolves the NFC form, so the check and the fetch can disagree about the host.","modified":"2026-09-03T16:04:21.814896553Z","published":"2026-08-31T18:17:00Z","upstream":["CVE-2026-19953"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-19953"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-19953"}],"affected":[{"package":{"name":"liburi-perl","ecosystem":"Ubuntu:14.04:LTS","purl":"pkg:deb/ubuntu/liburi-perl?arch=source&distro=trusty"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.60-1"],"ecosystem_specific":{"binaries":[{"binary_name":"liburi-perl","binary_version":"1.60-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-19953.json"}},{"package":{"name":"liburi-perl","ecosystem":"Ubuntu:16.04:LTS","purl":"pkg:deb/ubuntu/liburi-perl?arch=source&distro=xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.69-1","1.71-1"],"ecosystem_specific":{"binaries":[{"binary_name":"liburi-perl","binary_version":"1.71-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-19953.json"}},{"package":{"name":"liburi-perl","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/liburi-perl?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.72-1","1.72-2","1.73-1"],"ecosystem_specific":{"binaries":[{"binary_name":"liburi-perl","binary_version":"1.73-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-19953.json"}},{"package":{"name":"liburi-perl","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/liburi-perl?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.76-1","1.76-2"],"ecosystem_specific":{"binaries":[{"binary_version":"1.76-2","binary_name":"liburi-perl"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-19953.json"}},{"package":{"name":"liburi-perl","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/liburi-perl?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.08-1","5.10-1"],"ecosystem_specific":{"binaries":[{"binary_name":"liburi-perl","binary_version":"5.10-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-19953.json"}},{"package":{"name":"liburi-perl","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/liburi-perl?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.19-2","5.21-1","5.25-1","5.27-1"],"ecosystem_specific":{"binaries":[{"binary_version":"5.27-1","binary_name":"liburi-perl"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-19953.json"}},{"package":{"name":"liburi-perl","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/liburi-perl?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.30-1","5.34-2build1"],"ecosystem_specific":{"binaries":[{"binary_name":"liburi-perl","binary_version":"5.34-2build1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-19953.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N"},{"type":"Ubuntu","score":"medium"}]}