# CVE-2026-87823: zstd-jni 1.1.1 through 1.5.7-13 Out-of-Bounds Read via Direct ByteBuffer Frame-Size Methods

> Attackers can trigger out-of-bounds memory reads in zstd-jni via integer overflows, causing JVM crashes or data disclosure.

- **Severity:** High 8.8 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/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:** 9 Sep 2026
- **Also known as:** CLEANSTART-2026-BK85546, CLEANSTART-2026-CC37311, CLEANSTART-2026-RI59675, CLEANSTART-2026-UA88149, CLEANSTART-2026-UC40793, CLEANSTART-2026-VU34498, DEBIAN-CVE-2026-87823, GHSA-cm3p-487m-cmvq, GHSA-jfr6-9xqw-2g2q, UBUNTU-CVE-2026-87823

## What is CVE-2026-87823?

CVE-2026-87823 is a high-severity 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 performs 32-bit signed bounds checks on three direct-ByteBuffer frame-size native methods, allowing out-of-bounds memory reads via negative or overflowing offsets. Attackers can supply negative offset values near Integer.MIN_VALUE to read unmapped memory, causing JVM termination or extracting arbitrary frame size data from unintended memory locations.

Weakness: CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2026-87823?


## How do I fix CVE-2026-87823?

Upgrade to a fixed version.

## Is CVE-2026-87823 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-87823 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-87823 and fix it if it is affected.

What it is: CVE-2026-87823 is a high-severity 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: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-87823 exists.

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-2026-87823/ (Markdown: https://insights.sbomify.com/CVE-2026-87823/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-87823
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-87823
- OSV: https://osv.dev/vulnerability/CVE-2026-87823

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-87823/
Summaries are generated and may contain mistakes; the official description above is the record.