CVE-2026-89321: Software Security Vulnerability Vulnerability

MODERATE
Advisory Identifier: GHSA-ggqm-q66x-mqh3
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CVSS 4.3
CWE-409
Published
Advisory Summary

CVE-2026-89321 is a MODERATE (CVSS 4.3) security vulnerability vulnerability (CWE-409: Improper Handling of Highly Compressed Data (Data Amplification)) affecting Software libraries in the Maven ecosystem. The weakness occurs when the product does not handle or incorrectly handles a compressed input with a very high compression ratio that produces a large output.. Remediation is available in the latest vendor maintenance releases.

CVE-2026-89321 at a Glance

CVE Identifier CVE-2026-89321
GHSA Identifier GHSA-ggqm-q66x-mqh3
Severity MODERATE
CVSS v3.1 Base Score 4.3
CWE Classification CWE-409: Improper Handling of Highly Compressed Data (Data Amplification)
Affected Product Software
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 4.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability Low (A:L)

How to Fix CVE-2026-89321

To remediate this vulnerability, upgrade all affected Software dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2026-89321, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree

Analyze the terminal output to locate any version of Software in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: The mvn dependency:tree command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-409: Improper Handling of Highly Compressed Data (Data Amplification), where the product does not handle or incorrectly handles a compressed input with a very high compression ratio that produces a large output. In Software, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

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.

References

GitHub Advisory / Wiki ADVISORY
https://github.com/eclipse-openvsx/openvsx/security/advisories/GHSA-h685-gqw7-fqw7
NVD — CVE-2026-89321 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-89321
Software Source Repository REPOSITORY
https://github.com/eclipse-openvsx/openvsx/pull/2060

Frequently Asked Questions

What is CVE-2026-89321?
CVE-2026-89321 is a security vulnerability in Software classified as a security vulnerability vulnerability under CWE-409: Improper Handling of Highly Compressed Data (Data Amplification).
Which Software versions are affected?
Affected versions include releases prior to current release patches.
What version fixes CVE-2026-89321?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
What is the CVSS score of CVE-2026-89321?
CVE-2026-89321 has a CVSS v3.1 base score of 4.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L.
What CWE is associated with CVE-2026-89321?
CVE-2026-89321 is classified under CWE-409: Improper Handling of Highly Compressed Data (Data Amplification) (The product does not handle or incorrectly handles a compressed input with a very high compression ratio that produces a large output.).
How can I check Maven dependencies for CVE-2026-89321?
Run the dependency tree command: 'mvn dependency:tree'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-ggqm-q66x-mqh3",
  "modified" : "2026-09-14T09:31:03Z",
  "published" : "2026-09-14T09:31:03Z",
  "aliases" : [ "CVE-2026-89321" ],
  "details" : "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.\n\n\n\n\nOn 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.\n\n\n\n\nA 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.\n\n\n\n\nImpact 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.\n\n\n\n\nTriggering the extraction needs no authentication — only the upload does.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L"
  } ],
  "affected" : [ ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/eclipse-openvsx/openvsx/security/advisories/GHSA-h685-gqw7-fqw7"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-89321"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/eclipse-openvsx/openvsx/pull/2060"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-409" ],
    "severity" : "MODERATE",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-09-14T09:17:01Z"
  }
}