Parse Server has a stored XSS filter bypass via Content-Type MIME parameter and missing XML extension blocklist entries

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.3 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:L/VA:N/SC:H/SI:L/SA:N · score source

EPSS

• CVE-2026-32728: 0.28% estimated exploitation activity in the next 30 days; percentile 20.83 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact An attacker who is allowed to upload files can bypass the file extension filter by appending a MIME parameter (e.g. ;charset=utf-8) to the Content-Type header. This causes the extension validation to fail matching against the blocklist, allowing active content to be stored and served under the application's domain. In addition, certain XML-based file extensions that can render scripts in web browsers are not included in the default blocklist. This can lead to stored XSS attacks, compromising session tokens, user credentials, or other sensitive data accessible via the browser's local storage. Patches The fix strips MIME parameters from the Content-Type header before validating the file extension against the blocklist. The default blocklist has also been extended to include additional XML-based extensions (xsd, rng, rdf, rdf+xml, owl, mathml, mathml+xml) that can render active content in web browsers. Note that the fileUpload.fileExtensions option is intended to be configured as…

Published by the source

16 Mar 2026, 18:46 UTC

Last modified by the source

20 Mar 2026, 12:26 UTC

Source last checked

26 Oct 2026, 12:46 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-42ph-pf9q-cr72

2. Revision 2 · amended · 24 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-42ph-pf9q-cr72

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-32728

Advisory: Parse Server has a stored XSS filter bypass via Content-Type MIME parameter and missing XML extension blocklist entries
IDs: CVE-2026-32728, GHSA-42ph-pf9q-cr72
Record: https://patchnext.com/advisories/cve-2026-32728 (revision 3, source checked 26 Oct 2026, 12:46 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: parse-server 9.6.0-alpha.15, 8.6.41. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm parse-server: affected >= 9.0.0, < 9.6.0-alpha.15; < 8.6.41; fixed in 9.6.0-alpha.15, 8.6.41

## Suggested inspection (read-only)
- `npm ls parse-server --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on parse-server.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-42ph-pf9q-cr72 (OSV record GHSA-42ph-pf9q-cr72 lists affected ranges: npm parse-server >=9.0.0 =0 <8.6.41 (fixed))
- Verified: https://github.com/advisories/GHSA-42ph-pf9q-cr72 (GitHub-reviewed advisory GHSA-42ph-pf9q-cr72 lists affected ranges: npm parse-server >=9.0.0 =0 <8.6.41)

Commands are suggestions: review each one before running it.