CVE-2026-6322
Published: 05 May 2026
Summary
CVE-2026-6322 is a high-severity Interpretation Conflict (CWE-436) vulnerability in Openjsf Fast-Uri. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 1.9th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-2 (Flaw Remediation) and SC-7 (Boundary Protection).
Deeper analysis
CVE-2026-6322 is a vulnerability in the fast-uri JavaScript library's normalize() function, which incorrectly decodes percent-encoded authority delimiters within the host component and re-emits them as raw delimiters during serialization. This affects versions of fast-uri up to and including 3.1.1. Specifically, a maliciously crafted host combining an allowed domain, an encoded at-sign (@), and a different domain results in the normalized URI re-emitting the at-sign as a raw userinfo separator, effectively altering the URI's authority to the second domain. The issue is classified under CWE-436 with a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N).
Attackers can exploit this vulnerability remotely without authentication by supplying untrusted URLs to applications that invoke fast-uri's normalize() prior to performing host allowlist checks, redirect validation, or outbound request routing. Successful exploitation steers the application to a different authority than intended, potentially enabling open redirects, SSRF, or unintended network requests to attacker-controlled hosts.
Advisories from the OpenJS Foundation CNA and the fast-uri GitHub security advisory (GHSA-v39h-62p7-jpjc) recommend updating to fast-uri version 3.1.2 or later, where the normalization logic has been corrected to prevent decoding and re-emission of these delimiters in the host component.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-27248
Vulnerability details
fast-uri normalize() decoded percent-encoded authority delimiters inside the host component and then re-emitted them as raw delimiters during serialization. A host that combined an allowed domain, an encoded at-sign, and a different domain was re-emitted with the at-sign as a…
more
raw userinfo separator, changing the URI's authority to the second domain. Applications that normalize untrusted URLs before host allowlist checks, redirect validation, or outbound request routing can be steered to a different authority than the input appeared to specify. Versions <= 3.1.1 are affected. Update to 3.1.2 or later.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
CVE enables remote exploitation of public-facing apps (via malicious URL input to normalize() before allowlist/redirect/routing checks) for SSRF, open redirects and outbound connections to attacker hosts, directly mapping to T1190 for initial access and T1105 for resulting ingress of attacker-controlled content.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly addresses the CVE by requiring timely flaw remediation through updating the vulnerable fast-uri library to version 3.1.2 or later.
Mitigates exploitation by validating untrusted URL inputs for percent-encoded authority delimiters before normalization and host allowlist checks.
Boundary protection prevents SSRF and unintended outbound requests to attacker-controlled hosts by enforcing host-based access controls at application and network layers.