{"id":"DEBIAN-CVE-2026-87079","details":"Net::IDN::Punycode versions before 2.590 for Perl allow CPU exhaustion via quadratic insertion cost when decoding a long label in decode_punycode.  The XS backend inserts each decoded code point into a UTF-8 buffer and finds the insertion point by scanning that buffer from the start, one character at a time. The scan runs once per code point over the output built so far, so the cost is quadratic in the label length. The pure-Perl backend downgrades its input to bytes so that substr can index it directly, but takes its working copy before the downgrade, so when the input carries the UTF-8 flag every substr on the copy scans from the start, with the same quadratic cost.  Nothing bounds the label length in the to-Unicode direction. The 63-byte DNS limit is checked only when converting to ASCII, so domain_to_unicode and uts46_to_unicode pass an attacker-supplied label of any length to the decoder.","modified":"2026-09-23T05:01:22.222358470Z","published":"2026-09-22T08:16:40.637Z","upstream":["CVE-2026-87079"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-87079"}],"affected":[{"package":{"name":"libnet-idn-encode-perl","ecosystem":"Debian:12","purl":"pkg:deb/debian/libnet-idn-encode-perl?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.500-3","2.500-5"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-87079.json"}},{"package":{"name":"libnet-idn-encode-perl","ecosystem":"Debian:13","purl":"pkg:deb/debian/libnet-idn-encode-perl?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.500-5"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-87079.json"}},{"package":{"name":"libnet-idn-encode-perl","ecosystem":"Debian:14","purl":"pkg:deb/debian/libnet-idn-encode-perl?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.500-5"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-87079.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:N/I:N/A:H"}]}