# CVE-2016-15059: Net::IDN::Punycode versions before 2.301 for Perl allow a heap buffer overflow via unchecked writes past the output buffer in encode_punycode.

> Heap buffer overflow in Net::IDN::Punycode XS backend allows attackers to corrupt memory and potentially execute code via crafted input.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 22 Sep 2026
- **Updated:** 22 Sep 2026
- **Also known as:** DEBIAN-CVE-2016-15059, GHSA-6764-w6g6-m249, UBUNTU-CVE-2016-15059

## What is CVE-2016-15059?

CVE-2016-15059 is a critical memory corruption 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 2.301 for Perl allow a heap buffer overflow via unchecked writes past the output buffer in encode_punycode.

The XS backend builds the encoded label in the string buffer of the scalar it returns, sized from the input length. The loop that emits the digits of each code point checks for room before every write, but the write of the last digit of each round and the write of the terminating NUL do not, so an input whose encoded form fills the buffer writes past its end.

Only the XS backend is affected.

Encoding an attacker-supplied string corrupts the heap.

Weakness: CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2016-15059?


## How do I fix CVE-2016-15059?

Upgrade to a fixed version.

## Is CVE-2016-15059 being exploited?

There is no known exploitation of CVE-2016-15059 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2016-15059 and fix it if it is affected.

What it is: CVE-2016-15059 is a critical memory corruption 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-2016-15059 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-2016-15059/ (Markdown: https://insights.sbomify.com/CVE-2016-15059/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-15059
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-15059
- OSV: https://osv.dev/vulnerability/CVE-2016-15059

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From sbomify Insights: https://insights.sbomify.com/CVE-2016-15059/
Summaries are generated and may contain mistakes; the official description above is the record.