CVE-2026-74765 Net::IDN::Punycode versions before 2.590 for Perl allow an out-of-bounds read via integer overflow of the delta accumulator in encode_punycode.
An integer overflow in the XS backend allows out-of-bounds reads, potentially leaking memory or crashing the application when processing malicious IDN strings.
- 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-2026-74765?
CVE-2026-74765 is a medium-severity 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::Punycode versions before 2.590 for Perl allow an out-of-bounds read via integer overflow of the delta accumulator in encode_punycode.
The XS backend keeps the punycode delta, and the digit index derived from it, in a signed int. The accumulation `delta += (m-n) * (h+1)` has no overflow check, so a large enough code point wraps the delta and the digit index leaves the range of the 36-entry digit table. The bound before the final table access tests only for an index above 36, so a negative index passes it, as does 36 itself. Perl strings hold code points beyond the Unicode range, and one such code point overflows the accumulation on its own. Valid input wraps it as well, for example 1927 ASCII letters followed by U+10FFFF. The conversion functions encode a label before they check its length, so a long label reaches the encoder through the documented API.
Only the XS backend is affected.
Encoding an attacker-supplied string copies a byte from outside the digit table into the encoded result or crashes the process.
Which versions are affected by CVE-2026-74765?
How do I fix CVE-2026-74765?
No fix has been published for CVE-2026-74765 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-74765 being exploited?
There is no known exploitation of CVE-2026-74765 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-74765, GHSA-xw3q-mp5h-p8jx, UBUNTU-CVE-2026-74765.