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CVE-2026-87080

9.1 CRITICALpublic exploit available

Published 2026-09-22 · Updated 2026-09-22

AI risk analysis

Summary
The flaw allows a truncated label to be decoded incorrectly, leading to a different code point being derived. This can cause a sender to pick a label that resolves to a name on one installation but is rejected on another.
Exploitability
Exploitation is moderately hard as it requires crafting a specific label and sending it to a vulnerable system. Precondition is the presence of a system using an affected version of Net::IDN::Punycode::PP.
Blast radius
If exploited, it could lead to inconsistent resolution of domain names, potentially causing service disruptions or misrouting of traffic.
Detection
No reliable host or network indicator is derivable from the published description.
Prioritized remediation
Upgrade to Net::IDN::Punycode::PP version 2.590 or later.
parsingdecodingname-resolution

Analysis generated locally by qwen2.5:7b-instruct (no data left the box). AI-assisted — verify against primary sources before acting.

NVD 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.

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Weaknesses

CWE-1286

Public exploit & PoC references

All references

Source data: NVD (nvd.nist.gov), public domain. Exploit-DB.ai adds local AI analysis for defensive use only.

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