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.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
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
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.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-89321 being exploited?
There is no known exploitation of CVE-2026-89321 in the wild and no public exploit code.
Sources
Also known as GHSA-ggqm-q66x-mqh3, GHSA-h685-gqw7-fqw7.