# CVE-2026-39457: Stack overflow via select() file descriptor set overflow

> A stack overflow in libnv allows local attackers to corrupt memory and potentially escalate privileges to root.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 30 Apr 2026
- **Updated:** 1 May 2026
- **Also known as:** GHSA-gfv8-jx4x-32h7

## What is CVE-2026-39457?

CVE-2026-39457 is a high-severity memory corruption vulnerability in Freebsd Freebsd, published on 30 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

When exchanging data over a socket, libnv uses select(2) to wait for data to arrive.  However, it does not verify whether the provided socket descriptor fits in select(2)'s file descriptor set size limit of FD_SETSIZE (1024).

An attacker who is able to force a libnv application to allocate large file descriptors, e.g., by opening many descriptors and executing a program which is not careful to close them upon startup, can trigger stack corruption.  If the target application is setuid-root, then this could be used to elevate local privileges.

Weakness: CWE-121 (Stack-based Buffer Overflow)

## Which versions are affected by CVE-2026-39457?

It affects 1 product.


Products: Freebsd Freebsd.

## How do I fix CVE-2026-39457?

No fix has been published for CVE-2026-39457 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-39457 being exploited?

There is no known exploitation of CVE-2026-39457 in the wild and no public exploit code.

## Other vulnerabilities in Freebsd Freebsd

- [CVE-2018-17160](https://insights.sbomify.com/CVE-2018-17160/): Memory corruption in FreeBSD (critical 10.0)
- [CVE-2014-3954](https://insights.sbomify.com/CVE-2014-3954/): Memory corruption in n/a (critical 10.0)
- [CVE-2006-4304](https://insights.sbomify.com/CVE-2006-4304/): Memory corruption in n/a (critical 10.0)
- [CVE-2006-0226](https://insights.sbomify.com/CVE-2006-0226/): Integer overflow in n/a (critical 10.0)
- [CVE-2004-0002](https://insights.sbomify.com/CVE-2004-0002/): Denial of service in n/a (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-39457 and fix it if it is affected.

What it is: CVE-2026-39457 is a high-severity memory corruption vulnerability in Freebsd Freebsd, published on 30 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-39457 in the wild and no public exploit code.

Affected product: Freebsd Freebsd. 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-2026-39457/ (Markdown: https://insights.sbomify.com/CVE-2026-39457/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-39457
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-39457
- OSV: https://osv.dev/vulnerability/CVE-2026-39457

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-39457/
Summaries are generated and may contain mistakes; the official description above is the record.