ubuntu-cve-2026-19953
Vulnerability from osv_ubuntu
Published
2026-08-31 18:17
Modified
2026-09-03 13:12
Summary
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.
Severity
6.5 (Medium)
N/A (UNKNOWN)
References
| URL | Type | |
|---|---|---|
{
"affected": [
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "liburi-perl",
"binary_version": "1.60-1"
}
]
},
"package": {
"ecosystem": "Ubuntu:14.04:LTS",
"name": "liburi-perl",
"purl": "pkg:deb/ubuntu/liburi-perl@1.60-1?arch=source\u0026distro=trusty"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.60-1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "liburi-perl",
"binary_version": "1.71-1"
}
]
},
"package": {
"ecosystem": "Ubuntu:16.04:LTS",
"name": "liburi-perl",
"purl": "pkg:deb/ubuntu/liburi-perl@1.71-1?arch=source\u0026distro=xenial"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.69-1",
"1.71-1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "liburi-perl",
"binary_version": "1.73-1"
}
]
},
"package": {
"ecosystem": "Ubuntu:18.04:LTS",
"name": "liburi-perl",
"purl": "pkg:deb/ubuntu/liburi-perl@1.73-1?arch=source\u0026distro=bionic"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.72-1",
"1.72-2",
"1.73-1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "liburi-perl",
"binary_version": "1.76-2"
}
]
},
"package": {
"ecosystem": "Ubuntu:20.04:LTS",
"name": "liburi-perl",
"purl": "pkg:deb/ubuntu/liburi-perl@1.76-2?arch=source\u0026distro=focal"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.76-1",
"1.76-2"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "liburi-perl",
"binary_version": "5.10-1"
}
]
},
"package": {
"ecosystem": "Ubuntu:22.04:LTS",
"name": "liburi-perl",
"purl": "pkg:deb/ubuntu/liburi-perl@5.10-1?arch=source\u0026distro=jammy"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"5.08-1",
"5.10-1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "liburi-perl",
"binary_version": "5.27-1"
}
]
},
"package": {
"ecosystem": "Ubuntu:24.04:LTS",
"name": "liburi-perl",
"purl": "pkg:deb/ubuntu/liburi-perl@5.27-1?arch=source\u0026distro=noble"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"5.19-2",
"5.21-1",
"5.25-1",
"5.27-1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "liburi-perl",
"binary_version": "5.34-2build1"
}
]
},
"package": {
"ecosystem": "Ubuntu:26.04:LTS",
"name": "liburi-perl",
"purl": "pkg:deb/ubuntu/liburi-perl@5.34-2build1?arch=source\u0026distro=resolute"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"5.30-1",
"5.34-2build1"
]
}
],
"aliases": [],
"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.",
"id": "UBUNTU-CVE-2026-19953",
"modified": "2026-09-03T13:12:10Z",
"published": "2026-08-31T18:17:00Z",
"references": [
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2026-19953"
},
{
"type": "REPORT",
"url": "https://www.cve.org/CVERecord?id=CVE-2026-19953"
}
],
"related": [],
"schema_version": "1.7.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
],
"upstream": [
"CVE-2026-19953"
]
}
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Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
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.
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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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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