# CVE-2026-89321: Denial of service in Eclipse OpenVSX

> An attacker can upload a highly compressed VSIX to fill the server's temporary filesystem, causing denial of service for file requests.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 14 Sep 2026
- **Updated:** 14 Sep 2026
- **Also known as:** GHSA-ggqm-q66x-mqh3, GHSA-h685-gqw7-fqw7

## What is CVE-2026-89321?

CVE-2026-89321 is a medium-severity denial of service vulnerability in Eclipse OpenVSX, published on 14 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Publishing limits the compressed size of a VSIX (ovsx.publishing.max-content-size, 512 MB by default) but nothing limited how large an entry becomes when opened.

On the first request to /vscode/unpkg/{namespace}/{extension}/{version}/{path}, WebResourceService opened the entry with ZipFile.getInputStream() and passed the decompressed stream to Files.copy(), which ran to the end of the stream without counting bytes written. The result was cached under java.io.tmpdir, and that cache evicted by entry count (150), not by size, so it placed no bound on disk usage.

A publisher with access only to their own namespace could therefore upload a small, highly compressible VSIX and cause the server to write far larger files to the temp filesystem — repeating with different files or versions, since a repeat request is served from the cache.

Impact observed: the temp filesystem filled; requests for files not already cached returned 500 with No space left on device; a failed extraction left a partial cache file that blocked later attempts at that path; publishing failed with Failed to read extension file. Metadata and already-cached files kept working, and the server did not stop.

Triggering the extraction needs no authentication — only the upload does.

Weakness: CWE-409 (Improper Handling of Highly Compressed Data (Data Amplification))

## Which versions are affected by CVE-2026-89321?


## How do I fix CVE-2026-89321?

No fix has been published for CVE-2026-89321 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-89321 being exploited?

There is no known exploitation of CVE-2026-89321 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89321 and fix it if it is affected.

What it is: CVE-2026-89321 is a medium-severity denial of service vulnerability in Eclipse OpenVSX, published on 14 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-89321 in the wild and no public exploit code.

Affected product: Eclipse OpenVSX. 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-2026-89321/ (Markdown: https://insights.sbomify.com/CVE-2026-89321/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89321
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89321
- OSV: https://osv.dev/vulnerability/CVE-2026-89321

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89321/
Summaries are generated and may contain mistakes; the official description above is the record.