Vulnerability · Published Sep 22, 2026 · Assigned by CPANSec
CVE-2026-87078Net::IDN::Punycode versions from 2.302 before 2.590 for Perl leak the output buffer on every rejected label in decode_punycode
Critical 9.1
In plain English
A critical-severity memory leak in Net-IDN-Encode. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 34% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | libnet-idn-encode-perl | no fix listed | DEBIAN-CVE-2026-87078 |
| Debian:13 | libnet-idn-encode-perl | no fix listed | DEBIAN-CVE-2026-87078 |
| Debian:14 | libnet-idn-encode-perl | 2.600-1 | DEBIAN-CVE-2026-87078 |
| Ubuntu:22.04:LTS | libnet-idn-encode-perl | no fix listed | UBUNTU-CVE-2026-87078 |
| Ubuntu:24.04:LTS | libnet-idn-encode-perl | no fix listed | UBUNTU-CVE-2026-87078 |
| Ubuntu:26.04:LTS | libnet-idn-encode-perl | no fix listed | UBUNTU-CVE-2026-87078 |
| Ubuntu:26.10 | libnet-idn-encode-perl | no fix listed | UBUNTU-CVE-2026-87078 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Net-IDN-Encode | 2.302 – before 2.590 |
Weakness: CWE-401 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
References
- https://metacpan.org/release/PJCJ/Net-IDN-Encode-2.590-TRIAL/changes release-notes
- https://github.com/robrwo/Net-IDN-Encode/commit/92572f726e48af5559de4cc8a831463b79dfb217.patch patch
- https://github.com/robrwo/Net-IDN-Encode/commit/edad63e0eeeeb18d93bc6dfe4d9dcdff9c244e1b.patch patch
- http://www.openwall.com/lists/oss-security/2026/09/22/13