PatchTheCVECVE-2026-84394: fast-uri accepts a host that contains an unbalanced or misplaced authority bracket without reporting an error
CVE-2026-84394 is a high-severity flaw (CVSS 7.5) affecting fast-uri. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
fast-uri accepts a host that contains an unbalanced or misplaced authority bracket without reporting an error. A host that starts with an opening bracket but does not end with a closing bracket is neither validated as an IP literal nor canonicalized as a domain name, so parse() returns it as the host with error undefined, while Node's URL and the HTTP clients built on it resolve the same string to a different host. An application that reads the p
Why this priority
- High severity
- Remotely exploitable, no login, no user action
No fix is published yet: follow the downgrade or mitigation steps.
Risk facts
| CVSS score | 7.5 (High) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 0.4% (top 68%) |
| CISA exploited list | No |
| Weakness | CWE-436 |
| Published | 2026-09-03 |
| Last modified | 2026-09-04 |
Last updated 2026-09-04 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-84394?
fast-uri: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.
Is CVE-2026-84394 being exploited?
CVE-2026-84394 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-84394 affect?
CVE-2026-84394 affects fast-uri. Severity is high (CVSS 7.5). fast-uri accepts a host that contains an unbalanced or misplaced authority bracket without reporting an error. A host that starts with an opening bracket but does not end with a closing bracket is neither validated as an IP literal nor cano
How urgent is CVE-2026-84394?
Priority 39/100. High severity; Remotely exploitable, no login, no user action
Related CVEs
- CVE-2026-75931 HIGH 7.5 UPGRADE fast-uri is a URI parser for Node.js
- CVE-2026-76172 HIGH 7.5 UPGRADE fast-uri is a URI parser for Node.js
- CVE-2026-75899 HIGH 7.5 UPGRADE fast-uri is a URI parser for Node.js
- CVE-2026-75975 HIGH 7.5 UPGRADE fast-uri is a URI parser for Node.js
- CVE-2026-84292 HIGH 7.5 UPGRADE fast-uri serializes the port component of a URI without validating it