CVE-2026-87081 Net::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_ascii.
Attackers can cause CPU exhaustion in Perl applications using Net::IDN::UTS46 by submitting overlong labels with distinct non-ASCII characters.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-87081?
CVE-2026-87081 is a high-severity denial of service vulnerability, published on 22 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Net::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_ascii.
to_ascii punycode encodes each label and only then applies the 63-byte DNS limit. encode_punycode in both backends follows the sample implementation in RFC 3492, whose outer loop runs once per distinct non-ASCII code point and scans the whole input each round, so a label of distinct non-ASCII characters costs the square of its length before the limit rejects it. Every ASCII conversion in the distribution, including domain_to_ascii and email_to_ascii, goes through to_ascii.
Weakness: CWE-407
Which versions are affected by CVE-2026-87081?
How do I fix CVE-2026-87081?
No fix has been published for CVE-2026-87081 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-87081 being exploited?
There is no known exploitation of CVE-2026-87081 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-87081, GHSA-653x-rhrr-h9h8, UBUNTU-CVE-2026-87081.