# CVE-2026-2240: janet-lang janet compile.c janetc_pop_funcdef out-of-bounds

> A local attacker can trigger an out-of-bounds read in the Janet compiler, potentially causing crashes or arbitrary code execution.

- **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:** 9 Feb 2026
- **Updated:** 23 Feb 2026
- **Also known as:** GHSA-7wjv-672w-8j4q

## What is CVE-2026-2240?

CVE-2026-2240 is a medium-severity memory corruption vulnerability in janet-lang janet, published on 9 Feb 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A vulnerability has been found in janet-lang janet up to 1.40.1. The impacted element is the function janetc_pop_funcdef of the file src/core/compile.c. Such manipulation leads to out-of-bounds read. The attack must be carried out locally. The exploit has been disclosed to the public and may be used. The name of the patch is 4dd08a4cdef5b1c42d9a2c19fc24412e97ef51d5. A patch should be applied to remediate this issue.

Weakness: CWE-125 (Out-of-bounds Read), CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2026-2240?

It affects 1 product.


Products: Janet-Lang Janet.

## How do I fix CVE-2026-2240?

No fix has been published for CVE-2026-2240 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-2240 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-2240 exists.

## Other vulnerabilities in janet-lang janet

- [CVE-2022-30763](https://insights.sbomify.com/CVE-2022-30763/): Janet before 1.22.0 mishandles arrays. (high 7.5)
- [CVE-2026-2869](https://insights.sbomify.com/CVE-2026-2869/): janet-lang janet handleattr specials.c janetc_varset out-of-bounds (medium 4.8)
- [CVE-2026-2241](https://insights.sbomify.com/CVE-2026-2241/): janet-lang janet os.c os_strftime out-of-bounds (medium 4.8)
- [CVE-2026-2242](https://insights.sbomify.com/CVE-2026-2242/): janet-lang janet specials.c janetc_if out-of-bounds (medium 4.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-2240 and fix it if it is affected.

What it is: CVE-2026-2240 is a medium-severity memory corruption vulnerability in janet-lang janet, published on 9 Feb 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-2026-2240 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-2026-2240/ (Markdown: https://insights.sbomify.com/CVE-2026-2240/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-2240
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-2240
- OSV: https://osv.dev/vulnerability/CVE-2026-2240

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-2240/
Summaries are generated and may contain mistakes; the official description above is the record.