CVE-2026-87078

Name	CVE-2026-87078
Description	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.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
Debian Bugs	1148729

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
libnet-idn-encode-perl (PTS)	bookworm	2.500-3	vulnerable
	trixie	2.500-5	vulnerable
	forky, sid	2.502-1	vulnerable

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
libnet-idn-encode-perl	source	(unstable)	(unfixed)			1148729

Notes

https://lists.security.metacpan.org/cve-announce/msg/43753020/
Fixed by: https://github.com/robrwo/Net-IDN-Encode/commit/92572f726e48af5559de4cc8a831463b79dfb217 (v2.590-TRIAL)
Fixed by: https://github.com/robrwo/Net-IDN-Encode/commit/edad63e0eeeeb18d93bc6dfe4d9dcdff9c244e1b (v2.590-TRIAL)