# CVE-2026-87824: zstd-jni 1.3.3-1 through 1.5.7-13 Out-of-Bounds Read via Zstd.trainFromBufferDirect

> Attackers can cause JVM termination and read memory by supplying oversized sample lengths to the zstd-jni library's training function.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 9 Sep 2026
- **Updated:** 20 Sep 2026
- **Also known as:** CLEANSTART-2026-LG38764, CLEANSTART-2026-TA23513, CLEANSTART-2026-VB49028, CLEANSTART-2026-WM83029, CLEANSTART-2026-YT55390, CLEANSTART-2026-ZG93473, DEBIAN-CVE-2026-87824, GHSA-257p-3h6w-pg7h, GHSA-v36p-vv44-8qfg, UBUNTU-CVE-2026-87824

## What is CVE-2026-87824?

CVE-2026-87824 is a high-severity memory corruption vulnerability in luben zstd-jni, published on 9 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

zstd-jni before 1.5.7-14 fails to validate the samples buffer capacity in Zstd.trainFromBufferDirect, allowing attackers to read past buffer boundaries by supplying oversized per-sample lengths. Attackers can trigger out-of-bounds memory access by providing crafted sample length arrays that cause the native implementation to walk past the buffer allocation, resulting in JVM termination.

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

## Which versions are affected by CVE-2026-87824?


## How do I fix CVE-2026-87824?

Upgrade to a fixed version.

## Is CVE-2026-87824 being exploited?

There is no known exploitation of CVE-2026-87824 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-87824 and fix it if it is affected.

What it is: CVE-2026-87824 is a high-severity memory corruption vulnerability in luben zstd-jni, published on 9 Sep 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-2026-87824 in the wild and no public exploit code.

Affected product: luben zstd-jni. 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-2026-87824/ (Markdown: https://insights.sbomify.com/CVE-2026-87824/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-87824
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-87824
- OSV: https://osv.dev/vulnerability/CVE-2026-87824

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-87824/
Summaries are generated and may contain mistakes; the official description above is the record.