CVE-2026-30974: copyparty Volflag `nohtml` Did Not Block Vulnerability

MODERATE
Advisory Identifier: GHSA-m6hv-x64c-27mm
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CVSS 4.6
CWE-79
Published
Advisory Summary

CVE-2026-30974 is a MODERATE (CVSS 4.6) volflag `nohtml` did not block vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting copyparty libraries in the PyPI ecosystem. The issue involves volflag `nohtml` did not block javascript in svg files. Remediation is available by upgrading affected packages to version 1.20.11.

CVE-2026-30974 at a Glance

CVE Identifier CVE-2026-30974
GHSA Identifier GHSA-m6hv-x64c-27mm
Severity MODERATE
CVSS v3.1 Base Score 4.6
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product copyparty
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 4.6

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:R/S:U/C:L/I:L/A:N).

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

How to Fix CVE-2026-30974

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

copyparty fixed: 1.20.11 
pip install copyparty>=1.20.11
Verify Direct and Transitive Dependencies

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

pip show copyparty

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-30974, inspect your installed packages using pip:

pip show copyparty

Analyze the terminal output to locate any version of copyparty in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.20.11), your application is affected.

Note: The pip show copyparty command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'), where the product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. In copyparty, 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

### Summary The `nohtml` config option, intended to prevent execution of JavaScript in user-uploaded HTML files, did not apply to SVG images. ### Details A user with write-permission could upload an SVG containing embedded JavaScript, which would execute in the context of whichever user opens it. This in itself is not a vulnerability; it is intended behavior according to [the SVG spec](https://www.w3.org/TR/SVG11/script.html). The vulnerability is that the `nohtml` volflag, when enabled, did not prevent this. `nohtml`, intended for use on volumes which contains untrusted files, would correctly prevent execution of javascript in HTML files, but did not consider SVG images. This has been fixed in v1.20.11. ### Impact The malicious JavaScript could move or delete existing files on the server, or upload new files, using the account of the person who opens the SVG.

CVE-2026-30974 Affected copyparty Versions

1 component(s)
Fixed Versions:
1.20.11
Product / Package Ecosystem Affected Versions Fixed Version
copyparty
pypi/copyparty
PyPI
< 1.20.11
1.20.11

References

GitHub Advisory / Wiki ADVISORY
https://github.com/9001/copyparty/security/advisories/GHSA-m6hv-x64c-27mm
NVD — CVE-2026-30974 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-30974
Security Fix Commit FIX COMMIT
https://github.com/9001/copyparty/commit/1c9f894e149b6be3cc7de81efc93a4ce4766e0e5
copyparty Source Repository REPOSITORY
https://github.com/9001/copyparty
copyparty Release RELEASE
https://github.com/9001/copyparty/releases/tag/v1.20.11

Frequently Asked Questions

What is CVE-2026-30974?
CVE-2026-30974 is a security vulnerability in copyparty involving volflag `nohtml` did not block javascript in svg files under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which copyparty versions are affected?
Affected versions include releases prior to 1.20.11 across affected packages: copyparty.
What version fixes CVE-2026-30974?
Upgrading to 1.20.11 (or the latest patched release for your respective branch) resolves the vulnerability.
Is copyparty affected?
Yes, copyparty is affected in releases prior to 1.20.11. Upgrade your dependency to 1.20.11 or later.
What is the CVSS score of CVE-2026-30974?
CVE-2026-30974 has a CVSS v3.1 base score of 4.6 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N.
What CWE is associated with CVE-2026-30974?
CVE-2026-30974 is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.).
How can I check PyPI dependencies for CVE-2026-30974?
Run the dependency tree command: 'pip show copyparty'. 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-m6hv-x64c-27mm",
  "modified" : "2026-03-10T18:45:39Z",
  "published" : "2026-03-10T01:20:19Z",
  "aliases" : [ "CVE-2026-30974" ],
  "summary" : "copyparty: volflag `nohtml` did not block javascript in svg files",
  "details" : "### Summary\nThe `nohtml` config option, intended to prevent execution of JavaScript in user-uploaded HTML files, did not apply to SVG images.\n\n### Details\nA user with write-permission could upload an SVG containing embedded JavaScript, which would execute in the context of whichever user opens it.\n\nThis in itself is not a vulnerability; it is intended behavior according to [the SVG spec](https://www.w3.org/TR/SVG11/script.html). The vulnerability is that the `nohtml` volflag, when enabled, did not prevent this.\n\n`nohtml`, intended for use on volumes which contains untrusted files, would correctly prevent execution of javascript in HTML files, but did not consider SVG images. This has been fixed in v1.20.11.\n\n### Impact\nThe malicious JavaScript could move or delete existing files on the server, or upload new files, using the account of the person who opens the SVG.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "copyparty"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.20.11"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.20.10"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/9001/copyparty/security/advisories/GHSA-m6hv-x64c-27mm"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-30974"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/9001/copyparty/commit/1c9f894e149b6be3cc7de81efc93a4ce4766e0e5"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/9001/copyparty"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/9001/copyparty/releases/tag/v1.20.11"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-10T01:20:19Z",
    "nvd_published_at" : "2026-03-10T18:18:56Z"
  }
}