# CVE-2026-56018: Denial of service in JavaScript::Minifier::XS

> A memory leak in the JavaScript::Minifier::XS Perl library allows attackers to cause denial of service via unbounded memory growth during repeated minification calls.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 29 Jun 2026
- **Updated:** 29 Jun 2026
- **Also known as:** ALPINE-CVE-2026-56018, DEBIAN-CVE-2026-56018, GHSA-fvxv-8c37-qrc6, UBUNTU-CVE-2026-56018

## What is CVE-2026-56018?

CVE-2026-56018 is a high-severity denial of service vulnerability in GTERMARS JavaScript::Minifier::XS, published on 29 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

JavaScript::Minifier::XS versions before 0.16 for Perl leak memory on every call to minify(), allowing unbounded memory growth.

In JsMinify (XS.xs) the cleanup frees only the NodeSet structures and never the per-token contents buffers allocated in JsSetNodeContents; JsDiscardNode unlinks nodes without freeing their contents. Each token's contents buffer is therefore leaked on every call, and the two early returns taken when the node list is empty leak the whole NodeSet.

A long-lived process that minifies repeatedly, such as an asset pipeline or a server-side minifier endpoint, grows in memory without bound until it exhausts available memory and is killed, causing denial of service.

Weakness: CWE-401 (Missing Release of Memory after Effective Lifetime), CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2026-56018?


## How do I fix CVE-2026-56018?

Upgrade to a fixed version.

## Is CVE-2026-56018 being exploited?

There is no known exploitation of CVE-2026-56018 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-56018 and fix it if it is affected.

What it is: CVE-2026-56018 is a high-severity denial of service vulnerability in GTERMARS JavaScript::Minifier::XS, published on 29 Jun 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 CVE-2026-56018 in the wild and no public exploit code.

Affected product: GTERMARS JavaScript::Minifier::XS. 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-2026-56018/ (Markdown: https://insights.sbomify.com/CVE-2026-56018/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-56018
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-56018
- OSV: https://osv.dev/vulnerability/CVE-2026-56018

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-56018/
Summaries are generated and may contain mistakes; the official description above is the record.