Vulnerability · Published Sep 22, 2026 · Assigned by CPANSec
CVE-2026-87081Net::IDN::UTS46 versions before 2.590 for Perl allow CPU exhaustion via quadratic punycode encoding of an overlong label before the length check in to_ascii
High 7.5
In plain English
A high-severity security flaw in Net-IDN-Encode. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 32% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Net::IDN::UTS46 versions before 2.590 for Perl allow CPU exhaustion via quadratic punycode encoding of an overlong label before the length check in to_ascii. to_ascii punycode encodes each label and only then applies the 63-byte DNS limit. encode_punycode in both backends follows the sample implementation in RFC 3492, whose outer loop runs once per distinct non-ASCII code point and scans the whole input each round, so a label of distinct non-ASCII characters costs the square of its length before the limit rejects it. Every ASCII conversion in the distribution, including domain_to_ascii and email_to_ascii, goes through to_ascii.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | libnet-idn-encode-perl | no fix listed | DEBIAN-CVE-2026-87081 |
| Debian:13 | libnet-idn-encode-perl | no fix listed | DEBIAN-CVE-2026-87081 |
| Debian:14 | libnet-idn-encode-perl | 2.600-1 | DEBIAN-CVE-2026-87081 |
| Ubuntu:22.04:LTS | libnet-idn-encode-perl | no fix listed | UBUNTU-CVE-2026-87081 |
| Ubuntu:24.04:LTS | libnet-idn-encode-perl | no fix listed | UBUNTU-CVE-2026-87081 |
| Ubuntu:26.04:LTS | libnet-idn-encode-perl | no fix listed | UBUNTU-CVE-2026-87081 |
| Ubuntu:26.10 | libnet-idn-encode-perl | no fix listed | UBUNTU-CVE-2026-87081 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Net-IDN-Encode | 0 – before 2.590 |
Weakness: CWE-407 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
- https://metacpan.org/release/PJCJ/Net-IDN-Encode-2.590-TRIAL/changes release-notes
- https://github.com/robrwo/Net-IDN-Encode/commit/5ac3315131264670efcd3a29857b651506dfee8e.patch patch
- https://github.com/robrwo/Net-IDN-Encode/commit/ea34f812d7dc67f3b211f4d92e74c6a7e24d764a.patch patch
- http://www.openwall.com/lists/oss-security/2026/09/22/16