# 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.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 22 Sep 2026
- **Updated:** 22 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-74765, GHSA-xw3q-mp5h-p8jx, UBUNTU-CVE-2026-74765

## 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.

Weakness: CWE-190 (Integer Overflow or Wraparound), CWE-125 (Out-of-bounds Read)

## 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.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74765 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-74765 in the wild and no public exploit code.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-74765/ (Markdown: https://insights.sbomify.com/CVE-2026-74765/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74765
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74765
- OSV: https://osv.dev/vulnerability/CVE-2026-74765

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74765/
Summaries are generated and may contain mistakes; the official description above is the record.