SEPTEMBER 15, 2026
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Case File

CVE-2026-89321

MEDIUM · CVSS 4.3 EPSS 0.27% Public Exploit

Source: NVD + CISA KEV + EPSS · Published 2026-09-14 · Last synced 2026-09-15

CyberRota Analysis

AI-Generated

The vulnerability affects Java applications that handle VSIX files, allowing a malicious publisher to exploit the system by uploading a small, highly compressible VSIX file. This can lead to excessive disk usage on the server's temporary filesystem, potentially causing service disruptions, such as 500 errors due to lack of space. Organizations using Java-based services that allow VSIX uploads should prioritize addressing this issue to prevent potential denial-of-service conditions.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

Note: these links are listed for security research and verification purposes only.

CVE
CVE-2026-89321
Severity
MEDIUM
CVSS
4.3
EPSS
0.27%
Java

Original NVD 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.