# CVE-2026-0821: quickjs-ng quickjs quickjs.c js_typed_array_constructor heap-based overflow

> A heap-based buffer overflow in the quickjs-ng JavaScript engine allows remote attackers to execute arbitrary code or cause denial of service.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 10 Jan 2026
- **Updated:** 23 Feb 2026
- **Also known as:** ALPINE-CVE-2026-0821, DEBIAN-CVE-2026-0821, GHSA-rcpp-qhfh-r47v, UBUNTU-CVE-2026-0821

## What is CVE-2026-0821?

CVE-2026-0821 is a medium-severity memory corruption vulnerability in quickjs-ng quickjs, published on 10 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability was determined in quickjs-ng quickjs up to 0.11.0. This vulnerability affects the function js_typed_array_constructor of the file quickjs.c. Executing a manipulation can lead to heap-based buffer overflow. The attack may be launched remotely. The exploit has been publicly disclosed and may be utilized. This patch is called c5d80831e51e48a83eab16ea867be87f091783c5. A patch should be applied to remediate this issue.

Weakness: CWE-122 (Heap-based Buffer Overflow), CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2026-0821?

It affects 1 product.


Products: Quickjs-Ng Quickjs.

## How do I fix CVE-2026-0821?

Apply the vendor's patch.

## Is CVE-2026-0821 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-0821 exists.

## Other vulnerabilities in quickjs-ng quickjs

- [CVE-2025-46688](https://insights.sbomify.com/CVE-2025-46688/): Memory corruption in QuickJS (medium 5.6)
- [CVE-2026-1144](https://insights.sbomify.com/CVE-2026-1144/): quickjs-ng quickjs Atomics Ops quickjs.c use after free (medium 5.3)
- [CVE-2026-1145](https://insights.sbomify.com/CVE-2026-1145/): quickjs-ng quickjs quickjs.c js_typed_array_constructor_ta heap-based overflow (medium 5.3)
- [CVE-2026-0822](https://insights.sbomify.com/CVE-2026-0822/): quickjs-ng quickjs quickjs.c js_typed_array_sort heap-based overflow (medium 5.3)
- [CVE-2024-13903](https://insights.sbomify.com/CVE-2024-13903/): quickjs-ng QuickJS qjs quickjs.c JS_GetRuntime stack-based overflow (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-0821 and fix it if it is affected.

What it is: CVE-2026-0821 is a medium-severity memory corruption vulnerability in quickjs-ng quickjs, published on 10 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-0821 exists.

Affected product: quickjs-ng quickjs. 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-2026-0821/ (Markdown: https://insights.sbomify.com/CVE-2026-0821/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-0821
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-0821
- OSV: https://osv.dev/vulnerability/CVE-2026-0821

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-0821/
Summaries are generated and may contain mistakes; the official description above is the record.