# GHSA-jgvr-6x5w-hx5w: Zoo Design Studio: Recursive KCL parsing is vulnerable to denial-of-service

> Attackers can cause a denial of service by submitting deeply nested parentheses in KCL programs, crashing the parser via stack overflow.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 20 Aug 2026

## What is GHSA-jgvr-6x5w-hx5w?

GHSA-jgvr-6x5w-hx5w is a denial of service vulnerability in zoo-kcl, published on 20 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

### Impact
Feeding a KCL program that wraps an expression in deep, unnecessary parentheses triggers the parser’s recursive `expression` -> `unnecessarily_bracketed` -> `expression` path. With enough nesting, the call stack grows until it exceeds the process stack limit, causing a stack overflow.

## Which versions are affected by GHSA-jgvr-6x5w-hx5w?

4 open source packages ship an affected version, including zoo-kcl and kcl-lib.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `zoo-kcl` | PyPI | All versions | 0.3.129 |
| `zoo-kcl` | PyPI | All versions | 0.3.129 |
| `kcl-lib` | crates.io | All versions | 0.3.129 |
| `kcl-lib` | crates.io | All versions | 0.3.129 |

## How do I fix GHSA-jgvr-6x5w-hx5w?

Upgrade zoo-kcl to 0.3.129 or later.

## Is GHSA-jgvr-6x5w-hx5w being exploited?

There is no known exploitation of GHSA-jgvr-6x5w-hx5w in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GHSA-jgvr-6x5w-hx5w and fix it if it is affected.

What it is: GHSA-jgvr-6x5w-hx5w is a denial of service vulnerability in zoo-kcl, published on 20 Aug 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 GHSA-jgvr-6x5w-hx5w in the wild and no public exploit code.

Affected packages and fixed versions:
- zoo-kcl (PyPI): affected all versions; fixed in 0.3.129
- zoo-kcl (PyPI): affected all versions; fixed in 0.3.129
- kcl-lib (crates.io): affected all versions; fixed in 0.3.129
- kcl-lib (crates.io): affected all versions; fixed in 0.3.129

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/GHSA-jgvr-6x5w-hx5w/ (Markdown: https://insights.sbomify.com/GHSA-jgvr-6x5w-hx5w/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GHSA-jgvr-6x5w-hx5w

---
From sbomify Insights: https://insights.sbomify.com/GHSA-jgvr-6x5w-hx5w/
Summaries are generated and may contain mistakes; the official description above is the record.