UBUNTU-CVE-2026-87079 (CVE-2026-87079)
Vulnerability from osv_ubuntu – Published: 2026-09-22 08:16 – Updated: 2026-09-23 23:36 – Source website
VLAI
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.
Severity
7.5 (High)
N/A (UNKNOWN)
References
{
"affected": [
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libnet-idn-encode-perl",
"binary_version": "2.300-1build1"
}
]
},
"package": {
"ecosystem": "Ubuntu:16.04:LTS",
"name": "libnet-idn-encode-perl",
"purl": "pkg:deb/ubuntu/libnet-idn-encode-perl@2.300-1build1?arch=source\u0026distro=xenial"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.202-1",
"2.300-1",
"2.300-1build1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libnet-idn-encode-perl",
"binary_version": "2.400-1build1"
}
]
},
"package": {
"ecosystem": "Ubuntu:18.04:LTS",
"name": "libnet-idn-encode-perl",
"purl": "pkg:deb/ubuntu/libnet-idn-encode-perl@2.400-1build1?arch=source\u0026distro=bionic"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.400-1build1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libnet-idn-encode-perl",
"binary_version": "2.500-1build1"
}
]
},
"package": {
"ecosystem": "Ubuntu:20.04:LTS",
"name": "libnet-idn-encode-perl",
"purl": "pkg:deb/ubuntu/libnet-idn-encode-perl@2.500-1build1?arch=source\u0026distro=focal"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.500-1",
"2.500-1build1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libnet-idn-encode-perl",
"binary_version": "2.500-2build1"
}
]
},
"package": {
"ecosystem": "Ubuntu:22.04:LTS",
"name": "libnet-idn-encode-perl",
"purl": "pkg:deb/ubuntu/libnet-idn-encode-perl@2.500-2build1?arch=source\u0026distro=jammy"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.500-1build2",
"2.500-2",
"2.500-2build1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libnet-idn-encode-perl",
"binary_version": "2.500-5"
}
]
},
"package": {
"ecosystem": "Ubuntu:24.04:LTS",
"name": "libnet-idn-encode-perl",
"purl": "pkg:deb/ubuntu/libnet-idn-encode-perl@2.500-5?arch=source\u0026distro=noble"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.500-3",
"2.500-3build1",
"2.500-3build2",
"2.500-5"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libnet-idn-encode-perl",
"binary_version": "2.500-5build1"
}
]
},
"package": {
"ecosystem": "Ubuntu:26.04:LTS",
"name": "libnet-idn-encode-perl",
"purl": "pkg:deb/ubuntu/libnet-idn-encode-perl@2.500-5build1?arch=source\u0026distro=resolute"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.500-5build1"
]
}
],
"aliases": [],
"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.",
"id": "UBUNTU-CVE-2026-87079",
"modified": "2026-09-23T23:36:45Z",
"published": "2026-09-22T08:16:00Z",
"references": [
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2026-87079"
},
{
"type": "REPORT",
"url": "https://www.cve.org/CVERecord?id=CVE-2026-87079"
},
{
"type": "REPORT",
"url": "https://lists.security.metacpan.org/cve-announce/msg/43753023/"
},
{
"type": "REPORT",
"url": "https://github.com/robrwo/Net-IDN-Encode/commit/00d723423b66810af26b88c552bedc61975b3078.patch"
},
{
"type": "REPORT",
"url": "https://github.com/robrwo/Net-IDN-Encode/commit/447c6b38ef5d4570329fa4f78690f4e14e09ba0c.patch"
},
{
"type": "REPORT",
"url": "https://metacpan.org/release/PJCJ/Net-IDN-Encode-2.590-TRIAL/changes"
}
],
"related": [],
"schema_version": "1.7.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
],
"upstream": [
"CVE-2026-87079"
]
}
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vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
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The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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