CVE-2026-87080
CRITICALDescription
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.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Exploit Intelligence
Moderate risk: more likely to be exploited than 49% of all known CVEs.
References
Related Vulnerabilities
Other CWE-1286 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2024-7954 | Critical | 9.8 | 90% | - | Fix |
| CVE-2024-51983 | High | 7.5 | 12% | - | - |
| CVE-2024-51982 | High | 7.5 | 11% | - | - |
| CVE-2025-13878 | High | 7.5 | 9.2% | - | Fix |
| CVE-2026-21527 | High | 6.5 | 8.3% | - | Fix |
| CVE-2023-27043 | Medium | 5.3 | 2.5% | - | Fix |
Common questions
How do I fix CVE-2026-87080?
No published fix for CVE-2026-87080 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2026-87080 being actively exploited?
Not that we know of. CVE-2026-87080 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.63% is the estimated probability that it will be exploited in the next 30 days. That is higher than 49% of all scored CVEs.
How severe is CVE-2026-87080?
CVE-2026-87080 has a CVSS v3 base score of 9.1, rated critical. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-09-22.