# CVE-2026-0708: Libucl: libucl: denial of service via embedded null byte in ucl input

> A remote attacker can cause a denial of service in applications using libucl by providing crafted UCL input with embedded null bytes.

- **Severity:** High 8.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 17 Mar 2026
- **Updated:** 17 Mar 2026
- **Also known as:** GHSA-gxf2-jfmj-j5cj

## What is CVE-2026-0708?

CVE-2026-0708 is a high-severity denial of service vulnerability in libucl, published on 17 Mar 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

A flaw was found in libucl. A remote attacker could exploit this by providing a specially crafted Universal Configuration Language (UCL) input that contains a key with an embedded null byte. This can cause a segmentation fault (SEGV fault) in the `ucl_object_emit` function when parsing and emitting the object, leading to a Denial of Service (DoS) for the affected system.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-0708?

It affects 1 product.


Products: Vstakhov Libucl.

## How do I fix CVE-2026-0708?

No fix has been published for CVE-2026-0708 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-0708 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-0708 exists.

## Other vulnerabilities in libucl

- [CVE-2025-6499](https://insights.sbomify.com/CVE-2025-6499/): vstakhov libucl ucl_parser.c ucl_parse_multiline_string heap-based overflow (medium 4.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-0708 and fix it if it is affected.

What it is: CVE-2026-0708 is a high-severity denial of service vulnerability in libucl, published on 17 Mar 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-0708 exists.

Affected product: libucl. 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-2026-0708/ (Markdown: https://insights.sbomify.com/CVE-2026-0708/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-0708
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-0708
- OSV: https://osv.dev/vulnerability/CVE-2026-0708

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-0708/
Summaries are generated and may contain mistakes; the official description above is the record.