# CVE-2026-10268: janet-lang janet marsh.c unmarshal_one_fiber integer overflow

> A local attacker can trigger an integer overflow in the Janet language runtime's marshalling function, potentially causing a denial of service.

- **Severity:** Medium 4.8 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 1 Jun 2026
- **Updated:** 1 Jun 2026
- **Also known as:** GHSA-gqw4-cq8m-g989

## What is CVE-2026-10268?

CVE-2026-10268 is a medium-severity vulnerability in janet-lang janet, published on 1 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A weakness has been identified in janet-lang janet up to 1.41.0. This vulnerability affects the function unmarshal_one_fiber of the file src/core/marsh.c. Executing a manipulation can lead to integer overflow. It is possible to launch the attack on the local host. The exploit has been made available to the public and could be used for attacks. This patch is called d9b1d711ea1fde52ac73a82088b512a3e17bad0d. A patch should be applied to remediate this issue.

Weakness: CWE-190 (Integer Overflow or Wraparound), CWE-189

## Which versions are affected by CVE-2026-10268?


## How do I fix CVE-2026-10268?

No fix has been published for CVE-2026-10268 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-10268 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-10268 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-10268 and fix it if it is affected.

What it is: CVE-2026-10268 is a medium-severity vulnerability in janet-lang janet, published on 1 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-10268 exists.

Affected product: janet-lang janet. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-10268/ (Markdown: https://insights.sbomify.com/CVE-2026-10268/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-10268
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-10268
- OSV: https://osv.dev/vulnerability/CVE-2026-10268

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-10268/
Summaries are generated and may contain mistakes; the official description above is the record.