Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:NSummary
CVE-2026-6321 is a high-severity Path Traversal (CWE-22) 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 42th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to AC-3 (Access Enforcement) and SI-10 (Information Input Validation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-6321 is a path normalization vulnerability in the fast-uri JavaScript library, affecting versions up to and including 3.1.0. The issue arises because the library's normalize() and equal() functions decode percent-encoded path separators and dot segments before applying dot-segment removal. This causes encoded path data to be treated as real slashes and parent-directory references, allowing distinct URIs to collapse onto the same normalized path. Applications relying on fast-uri to normalize or compare attacker-controlled URLs for path-based access control policies are vulnerable to bypasses where a seemingly confined path normalizes to an unintended location. The vulnerability is rated 7.5 on the CVSS v3.1 scale (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N) and maps to CWE-22 (Improper Limitation of a Pathname to a Restricted Directory).
Attackers can exploit this vulnerability remotely over the network with low complexity and no privileges or user interaction required. By crafting a URL with percent-encoded path separators or dot segments (such as encoded slashes or "../" sequences), an attacker can trick the normalization process into resolving to a path outside the intended prefix. This enables bypass of security policies that check URLs against allowed directories, potentially allowing unauthorized access to sensitive files or endpoints in applications using fast-uri for URL handling.
Advisories from the OpenJS Foundation CNA and the fast-uri GitHub security advisory recommend updating to version 3.1.1 or later, where the decoding order is fixed to prevent premature interpretation of encoded segments.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-27129
Vulnerability Data
fast-uri decoded percent-encoded path separators and dot segments before applying dot-segment removal in its normalize() and equal() functions. Encoded path data was treated like real slashes and parent-directory references, so distinct URIs could collapse onto the same normalized path. Applications…
more
that normalize or compare attacker-controlled URLs to enforce path-based policy can be bypassed, with a path that appears confined under an allowed prefix normalizing to a different location. Versions <= 3.1.0 are affected. Update to 3.1.1 or later.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V5.3.2
Mitigating Controls (NIST 800-53 r5) AI
Enforces the intended directory access authorizations that path traversal would otherwise bypass.
Input validation directly neutralizes special path elements before pathname construction occurs.
Least privilege reduces the impact of any unauthorized file access obtained via traversal.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Patching/maintenance can remediate known path-traversal flaws in deployed software (partial prevention of exploitability) but does nothing to stop the coding defect from being introduced in the first place.
PR.AA-05 defines and reviews access policies but does not address code-level pathname neutralization, so neither direction prevents CWE-22.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development catches path traversal via static/dynamic analysis.
Secure SDLC mandates input validation and path sanitization that directly prevent path traversal.
Application security requirements include rules for safe file handling and canonicalization.
Secure architecture principles require least-privilege file access and directory isolation.
Secure coding standards explicitly forbid unsafe path construction and mandate safe APIs.
Information access restriction limits which files an application may read or write.