CVE-2026-55778
Parse Server: Stored XSS via non-standard file extension bypassing file upload extension blocklist
- Published
- Updated
- Reserved
- Assigned by
- GitHub_M
Description
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.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 4.0 | Low2.1 | 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 |
| NVDNVD · Deferred | 4.0 | Low2.1 | 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 (exploitation in 30 days)
- 0.55% · top 54% of all CVEs (6 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Low 2.1.
Weakness
Affected products
parse-community · parse-server
- affected >= 9.0.0-alpha.1, < 9.9.1-alpha.11
- affected < 8.6.81
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- npmparse-serverGHSA-v8x7-r927-cc93 (opens in a new tab)
References (7)
- https://github.com/parse-community/parse-server/security/advisories/GHSA-v8x7-r927-cc93 (opens in a new tab)x_refsource_CONFIRM
- https://github.com/parse-community/parse-server/pull/10505 (opens in a new tab)x_refsource_MISC
- https://github.com/parse-community/parse-server/pull/10506 (opens in a new tab)x_refsource_MISC
- https://github.com/parse-community/parse-server/commit/97c6a78d19f976ec756c1295f08a8fccab90799a (opens in a new tab)x_refsource_MISC
- https://github.com/parse-community/parse-server/commit/be12a60d65b6e140481882037fb896b1f951df50 (opens in a new tab)x_refsource_MISC
- https://github.com/parse-community/parse-server/releases/tag/8.6.81 (opens in a new tab)x_refsource_MISC
- https://github.com/parse-community/parse-server/releases/tag/9.9.1-alpha.11 (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-v8x7-r927-cc93 (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-55778)Record last updated .