CVE-2026-27818
TerriaJS-Server has a domain validation bypass vulnerability in its proxy allowlist
Description
### Impact A validation bug allows an attacker to proxy domains not explicitly allowed in the `proxyableDomains` configuration. The validation only checks if a hostname _ended_ with an allowed domain. This meant: If `example.com` is allowed in `proxyableDomains`: - ✅ example.com is allowed (correct) - ✅ api.example.com is allowed (correct) - ⚠️ maliciousexample.com is allowed (incorrect) An attacker could register maliciousexample.com and proxy content through `terriajs-server`, bypassing proxy restrictions. ### Patches All versions up to 4.0.2 are affected. Upgrade to 4.0.3 to address the vulnerability.
How to fix CVE-2026-27818
To remediate CVE-2026-27818, upgrade the affected package to a fixed version below.
- —upgrade to 4.0.3 or later
Is CVE-2026-27818 being exploited?
Low — EPSS is 0.1%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- from 0, < 4.0.3
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 4.0 | — | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N |