CVE-2026-55778

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

CVSS 2.1 LOWCWE-434

Vexday Risk Score

5Low

SSVC decision (CISA)

Track

No exploitation signal → monitor

CVSS 2.1EPSS —KEV nãoPoC —Nuclei —Metasploit —Patch —

Lifecycle

08 Jul 2026Published on NVD

Recommendation: Monitor — no exploitation signal at the moment.

Parse 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.

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

Affected products

parse-community · parse-server

References

https://github.com/parse-community/parse-server/commit/97c6a78d19f976ec756c1295f08a8fccab90799a https://github.com/parse-community/parse-server/commit/be12a60d65b6e140481882037fb896b1f951df50 https://github.com/parse-community/parse-server/pull/10505 https://github.com/parse-community/parse-server/pull/10506 https://github.com/parse-community/parse-server/releases/tag/8.6.81 https://github.com/parse-community/parse-server/releases/tag/9.9.1-alpha.11 https://github.com/parse-community/parse-server/security/advisories/GHSA-v8x7-r927-cc93