CVE-2026-35200
LOW
GHSA-vr5f-2r24-w5hc
CVSS Vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/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
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3Tags
Description
### Impact A file can be uploaded with a filename extension that passes the file extension allowlist (e.g., `.txt`) but with a `Content-Type` header that differs from the extension (e.g., `text/html`). The `Content-Type` is passed to the storage adapter without consistency validation. Storage adapters that store and serve the provided Content-Type (such as S3 or GCS) serve the file with the mismatched Content-Type. The default GridFS adapter is not affected because it derives Content-Type from the filename at serving time. ### Patches The file upload now derives the Content-Type from the filename extension, overriding any user-provided Content-Type when the file has an extension. ### Workarounds Configure the storage adapter or CDN to derive Content-Type from the filename extension instead of using the stored Content-Type.
Analysis
Parse Server file upload handler fails to validate Content-Type headers against filename extensions, allowing attackers to upload files with benign extensions (e.g., .txt) but malicious MIME types (e.g., text/html) that are served with the user-supplied Content-Type by cloud storage adapters like S3 and GCS. This enables content-type confusion attacks such as reflected XSS when files are served through CDNs or web servers that trust the stored Content-Type header. …
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