CPANSA-Net-IDN-Encode-2026-87080: Net-IDN-Encode vulnerability
| Publisher | giterlizzi | Document category | csaf_security_advisory |
|---|---|---|---|
| Initial release date | 2026-09-22T00:00:00 | Engine | CSAF Perl Toolkit 0.26 |
| Current release date | 2026-09-22T00:00:00 | Build Date | |
| Current version | 1 | Status | final |
| CVSS v3.1 Base Score | 9.1 | Severity | Critical |
| Original language | Language | en | |
| Also referred to | |||
Vulnerability Description
Net::IDN::Punycode::PP versions before 2.590 for Perl decode a truncated label to a name containing a character it never encoded in decode_punycode.
The pure-Perl decoder reads one digit at a time with four-argument substr and tests the result with defined to detect the end of the input. substr on an exhausted string returns the empty string rather than undef, so decoding continues past the end. The empty string converts to a digit value below the range, reducing the accumulator, and the decoder derives one extra code point and its position from it. The result is deterministic. The XS backend rejects the same label.
Net::IDN::Punycode uses this backend wherever the XS does not build.
The two backends disagree about what such a label means, so a sender can pick a label that one installation resolves to a name and another rejects.
Vulnerabilities
CVE-2026-87080
Vulnerability DescriptionNet::IDN::Punycode::PP versions before 2.590 for Perl decode a truncated label to a name containing a character it never encoded in decode_punycode.
The pure-Perl decoder reads one digit at a time with four-argument substr and tests the result with defined to detect the end of the input. substr on an exhausted string returns the empty string rather than undef, so decoding continues past the end. The empty string converts to a digit value below the range, reducing the accumulator, and the decoder derives one extra code point and its position from it. The result is deterministic. The XS backend rejects the same label.
Net::IDN::Punycode uses this backend wherever the XS does not build.
The two backends disagree about what such a label means, so a sender can pick a label that one installation resolves to a name and another rejects.
| Weakness | CWE-1286 : Improper Validation of Syntactic Correctness of Input |
|---|
Product status
Known affected
| Product | Score | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Net-IDN-Encode less than 2.590 |
|
Fixed
- Net-IDN-Encode greater than or equal 2.590
giterlizzi
Namespace: https://github.com/giterlizzi/
gdt@cpan.org
References
- CPANSA-Net-IDN-Encode-2026-87080 JSON self
https://raw.githubusercontent.com/giterlizzi/perl-CPANSA-CSAF/develop/csaf/white/2026/cpansa-net-idn-encode-2026-87080.json - https://github.com/robrwo/Net-IDN-Encode/commit/48436c7ad2c4d4c6398110e11133754fc476a783.patch external
https://github.com/robrwo/Net-IDN-Encode/commit/48436c7ad2c4d4c6398110e11133754fc476a783.patch - https://metacpan.org/release/PJCJ/Net-IDN-Encode-2.590-TRIAL/changes external
https://metacpan.org/release/PJCJ/Net-IDN-Encode-2.590-TRIAL/changes - http://www.openwall.com/lists/oss-security/2026/09/22/15 external
http://www.openwall.com/lists/oss-security/2026/09/22/15 - CVE-2026-87080 (NVD) external
https://nvd.nist.gov/vuln/detail/CVE-2026-87080
Revision history
| Version | Date of the revision | Summary of the revision |
|---|---|---|
| 1 | Tue Sep 22 00:00:00 2026 | First release |
Sharing rules
TLP:WHITE
For the TLP version see: https://www.first.org/tlp/