CVE-2026-87078: critical vulnerability in Net-IDN-Encode
Net::IDN::Punycode versions from 2.302 before 2.590 for Perl leak the output buffer on every rejected label in decode_punycode
Published
28Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 9.1epss 0.7%
exploitation probability
0.7%top 50% of all CVEs
observed exploitation
nono source reports it
Net::IDN::Punycode versions from 2.302 before 2.590 for Perl leak the output buffer on every rejected label in decode_punycode.
The XS backend allocates the scalar it returns before it validates the input, sizing the buffer at twice the input length. The scalar is released only on the success path, so each of the three croaks that reject a label leaves the scalar and its buffer allocated. Nothing bounds the label length in the to-Unicode direction, since the 63-byte DNS limit is checked only when converting to ASCII.
Only the XS backend is affected.
A sender who supplies invalid labels grows the process by twice the label length per rejected call, with no successful call needed.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Affected products
Net-IDN-EncodeRelated CVEs — Net-IDN-Encode
In the same product, most dangerous first.
CVE-2026-87082HIGHNet::IDN::Punycode versions before 2.590 for Perl hang, crash or return a wrong label via unvalidated malformed UTF-8 in encode_punycodeEPSS 0.7%CVE-2026-87080CRITICALNet::IDN::Punycode::PP versions before 2.590 for Perl decode a truncated label to a name containing a character it never encoded in decode_punycodeEPSS 0.6%CVE-2026-87081HIGHNet::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_asciiEPSS 0.6%CVE-2026-87079HIGHNet::IDN::Punycode versions before 2.590 for Perl allow CPU exhaustion via quadratic insertion cost when decoding a long label in decode_punycodeEPSS 0.6%CVE-2026-74765MEDIUMNet::IDN::Punycode versions before 2.590 for Perl allow an out-of-bounds read via integer overflow of the delta accumulator in encode_punycodeEPSS 0.5%CVE-2016-15059CRITICALNet::IDN::Punycode versions before 2.301 for Perl allow a heap buffer overflow via unchecked writes past the output buffer in encode_punycodeEPSS 0.4%
References
https://github.com/robrwo/Net-IDN-Encode/commit/92572f726e48af5559de4cc8a831463b79dfb217.patchhttps://github.com/robrwo/Net-IDN-Encode/commit/edad63e0eeeeb18d93bc6dfe4d9dcdff9c244e1b.patchhttps://metacpan.org/release/PJCJ/Net-IDN-Encode-2.590-TRIAL/changeshttp://www.openwall.com/lists/oss-security/2026/09/22/13