CVE-2026-32728: Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to 9.6.0-alpha.15 and 8.6.41, an attacke...

Description

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to 9.6.0-alpha.15 and 8.6.41, 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. The fix in versions 9.6.0-alpha.15 and 8.6.41 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 an allowlist of file extensions that are valid for a specific application, not as a denylist. The default denylist is provided only as a basic default that covers most common problematic extensions. It is not intended to be an exhaustive list of all potentially dangerous extensions. Developers should not rely on the default value, as new extensions that can render active content in browsers might emerge in the future. As a workaround, configure the `fileUpload.fileExtensions` option to use an allowlist of only the file extensions that your application needs, rather than relying on the default blocklist.

Metrics

CVSS 3.1

7.6/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N

CVSS 4.0

8.3/10

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability

0.27%

18.9th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-79

Affected Software

Vendor	Product	Versions	Update
Parseplatform	Parse-Server	< 8.6.41	—
Parseplatform	Parse-Server	>= 9.0.0, < 9.6.0	—
Parseplatform	Parse-Server	9.6.0	Alpha1

References

Timeline

Published: Mar 18, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-32728?

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to 9.6.0-alpha.15 and 8.6.41, 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. The fix in versions 9.6.0-alpha.15 and 8.6.41 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 an allowlist of file extensions that are valid for a specific application, not as a denylist. The default denylist is provided only as a basic default that covers most common problematic extensions. It is not intended to be an exhaustive list of all potentially dangerous extensions. Developers should not rely on the default value, as new extensions that can render active content in browsers might emerge in the future. As a workaround, configure the `fileUpload.fileExtensions` option to use an allowlist of only the file extensions that your application needs, rather than relying on the default blocklist.

How severe is CVE-2026-32728?

CVE-2026-32728 has a CVSS score of 8.3/10 (HIGH severity). The EPSS model estimates a 0.27% probability of exploitation in the next 30 days.

How do I fix CVE-2026-32728?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.