{"id":"CVE-2026-87079","published":"2026-09-22T08:16:40.637","lastModified":"2026-09-22T19:07:00.983","description":"Net::IDN::Punycode versions before 2.590 for Perl allow CPU exhaustion via quadratic insertion cost when decoding a long label in decode_punycode.\n\nThe 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.\n\nNothing 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.","cvssScore":7.5,"cvssSeverity":"HIGH","cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cwes":["CWE-407"],"vendors":[],"products":[],"references":[{"url":"https://github.com/robrwo/Net-IDN-Encode/commit/00d723423b66810af26b88c552bedc61975b3078.patch","tags":[]},{"url":"https://github.com/robrwo/Net-IDN-Encode/commit/447c6b38ef5d4570329fa4f78690f4e14e09ba0c.patch","tags":[]},{"url":"https://metacpan.org/release/PJCJ/Net-IDN-Encode-2.590-TRIAL/changes","tags":[]},{"url":"http://www.openwall.com/lists/oss-security/2026/09/22/14","tags":[]}],"exploitRefs":[{"url":"https://github.com/robrwo/Net-IDN-Encode/commit/00d723423b66810af26b88c552bedc61975b3078.patch","tags":[]},{"url":"https://github.com/robrwo/Net-IDN-Encode/commit/447c6b38ef5d4570329fa4f78690f4e14e09ba0c.patch","tags":[]}],"hasPoc":true,"ai":{"summary":"A CPU exhaustion vulnerability exists in Net::IDN::Punycode Perl module versions before 2.590, where decoding long domain labels causes quadratic time complexity due to inefficient buffer insertion operations. This allows attackers to consume excessive CPU resources when processing specially crafted domain names.","exploitability":"Exploitation is relatively straightforward as it requires only sending a maliciously crafted long domain label to trigger the quadratic CPU cost, with no additional preconditions needed.","blast_radius":"The vulnerability could affect any system processing IDN domain names through this Perl module, potentially causing widespread service degradation or denial of service across web applications, email servers, and DNS services using the affected library.","remediation":"Upgrade to 2.590 or later","detection":"No reliable host or network indicator is derivable from the published description.","tags":["dos","cpu","perl","idn"],"model":"garnet-coder","analyzedAt":"2026-10-18T16:14:50.588Z"}}