High
libnet-idn-encode-perl — security advisory
Net::IDN::Punycode versions from 2.301 before 2.590 for Perl allow a heap use-after-free via a decoded code point that reallocates the output buffer in decode_punycode. The XS backend inserts each decoded code point into the string buffer of the scalar it returns. decode_punycode computes the insertion pointer first and only then grows the buffer when the code point does not fit. The growth reallocates the buffer and updates every pointer except the insertion pointer, so the move that follows and the write of the code point go through a freed pointer. The buffer starts at twice the label length, and a code point above U+FFFF takes four bytes in the output, so a label of such code points outgrows it and forces the reallocation. Version 2.301, the fix for CVE-2016-15059, introduced the defect. Only the XS backend is affected. Decoding an attacker-supplied punycode label reads and writes freed heap memory.
- Products
- libnet-idn-encode-perl
- Affected versions
- 2.202-1, 2.300-1, 2.300-1build1, 2.400-1build1, 2.500-1, 2.500-1build1, 2.500-1build2, 2.500-2, 2.500-2build1, 2.500-3, 2.500-3build1, 2.500-3build2, 2.500-5, 2.500-5build1, 2.500-5build2
- Fixed versions
- Not specified
- CVEs
- CVE-2026-74766
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 03:16 UTC · Revision 1
Source evidence
Net::IDN::Punycode versions from 2.301 before 2.590 for Perl allow a heap use-after-free via a decoded code point that reallocates the output buffer in decode_punycode. The XS backend inserts each decoded code point into the string buffer of the scalar it returns. decode_punycode computes the insertion pointer first and only then grows the buffer when the code point does not fit. The growth reallocates the buffer and updates every pointer except the insertion pointer, so the move that follows and the write of the code point go through a freed pointer. The buffer starts at twice the label length, and a code point above U+FFFF takes four bytes in the output, so a label of such code points outgrows it and forces the reallocation. Version 2.301, the fix for CVE-2016-15059, introduced the defect. Only the XS backend is affected. Decoding an attacker-supplied punycode label reads and writes freed heap memory.
osv:UBUNTU-CVE-2026-74766
libnet-idn-encode-perl
Fixed versions: Not specified
libnet-idn-encode-perl
Fixed versions: Not specified
libnet-idn-encode-perl
Fixed versions: Not specified
libnet-idn-encode-perl
Fixed versions: Not specified
libnet-idn-encode-perl
Fixed versions: Not specified
libnet-idn-encode-perl
Fixed versions: Not specified
libnet-idn-encode-perl
Fixed versions: Not specified
Complete source record
{
"id": "4a1a7576c06f1fc0a0cc5e08388e331202d521623da7489b805e454652254569",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-74766",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "UBUNTU-CVE-2026-74766",
"summary": "Net::IDN::Punycode versions from 2.301 before 2.590 for Perl allow a heap use-after-free via a decoded code point that reallocates the output buffer in decode_punycode. The XS backend inserts each decoded code point into the string buffer of the scalar it returns. decode_punycode computes the insertion pointer first and only then grows the buffer when the code point does not fit. The growth reallocates the buffer and updates every pointer except the insertion pointer, so the move that follows and the write of the code point go through a freed pointer. The buffer starts at twice the label length, and a code point above U+FFFF takes four bytes in the output, so a label of such code points outgrows it and forces the reallocation. Version 2.301, the fix for CVE-2016-15059, introduced the defect. Only the XS backend is affected. Decoding an attacker-supplied punycode label reads and writes freed heap memory.",
"evidence": "osv:UBUNTU-CVE-2026-74766",
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"severity": "high",
"structured": {
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"aliases": [
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"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
},
{
"type": "Ubuntu",
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},
"versions": [
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},
"versions": [
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],
"modified": "2026-10-17T13:01:05.043699961Z",
"provider": "osv",
"upstream": [
"CVE-2026-74766"
],
"references": [
"https://ubuntu.com/security/CVE-2026-74766",
"https://www.cve.org/CVERecord?id=CVE-2026-74766",
"https://lists.security.metacpan.org/cve-announce/msg/43753027/",
"https://github.com/robrwo/Net-IDN-Encode/commit/259e74c5739175b063c5393a4ce4a0705678ba61.patch",
"https://github.com/robrwo/Net-IDN-Encode/commit/2fbc71e4d8517ab65c5d5d35fda086371b735a3f.patch",
"https://metacpan.org/release/PJCJ/Net-IDN-Encode-2.590-TRIAL/changes",
"https://www.cve.org/CVERecord?id=CVE-2016-15059"
]
},
"related_cves": [
{
"value": "CVE-2026-74766",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 360942,
"published_at": "2026-09-22T08:16:00+00:00"
}