Parse Server: Stored XSS via non-standard file extension bypassing file upload extension blocklist

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Summary

CVECVE-2026-55778
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-08 21:16:50 UTC
Updated2026-07-10 19:06:45 UTC
DescriptionParse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to 9.9.1-alpha.11 and 8.6.81, the default fileUpload.fileExtensions blocklist could be bypassed by uploading a file with a non-standard or compound extension and dangerous content type, allowing storage adapters such as S3 and GCS to serve attacker-supplied active content and enable stored cross-site scripting. This issue is fixed in versions 9.9.1-alpha.11 and 8.6.81.

Risk And Classification

Primary CVSS: v4.0 2.1 LOW from [email protected]

CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:L/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

EPSS: 0.004060000 probability, percentile 0.326510000 (date 2026-07-12)

Problem Types: CWE-434 | CWE-434 CWE-434: Unrestricted Upload of File with Dangerous Type

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary2.1LOWCVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N/E:X/C...
4.0CNADECLARED2.1LOWCVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
Present
Privileges Required
Low
User Interaction
Passive
Confidentiality
None
Integrity
Low
Availability
None
Sub Conf.
Low
Sub Integrity
Low
Sub Availability
None

CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:L/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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Parse-community Parse-server affected >= 9.0.0-alpha.1, < 9.9.1-alpha.11 Not specified
CNA Parse-community Parse-server affected < 8.6.81 Not specified

References

ReferenceSourceLinkTags
github.com/parse-community/parse-server/pull/10505 [email protected] github.com
github.com/parse-community/parse-server/pull/10506 [email protected] github.com
github.com/parse-community/parse-server/releases/tag/9.9.1-alpha.11 [email protected] github.com
github.com/parse-community/parse-server/commit/be12a60d65b6e140481882037... [email protected] github.com
github.com/parse-community/parse-server/releases/tag/8.6.81 [email protected] github.com
github.com/parse-community/parse-server/security/advisories/GHSA-v8x7-r9... [email protected] github.com
github.com/parse-community/parse-server/commit/97c6a78d19f976ec756c1295f... [email protected] github.com
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