CVE-2026-6321

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 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.

What this means for your business

It affects Openjsf Fast-Uri. It matters if your company, or a supplier that handles your data, runs it.
An attacker can use it remotely, over a network, without a login, and without anyone at your company clicking anything.
FIRST's prediction model gives it a 0.6% chance of attack attempts being seen in the next 30 days, ranking above 48% of all known flaws.

What to do

1Check whether your company or your suppliers run Openjsf Fast-Uri, and which version. The affected versions are listed further down this page.
2If you do, apply the vendor's fix. A patch or vendor advisory has been published.

Not sure if your company is exposed?

Fastnexa’s certified penetration testers can check whether attackers could use this flaw, or others like it, against your websites, apps and network. The full test is free for our first 10 founding clients until 31 December 2026.

Check if you’re exposed Book a call

Scoring

CVSS: 7.5 (v3.1)
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weakness: CWE-22
Assigned by: ce714d77-add3-4f53-aff5-83d477b104bb

Dates

Published: 2026-05-04
Last modified: 2026-09-10
Sources: NVD

Affected products

Openjsf Fast-Uri- 3.1.1

As listed in the NVD configuration data. Not a statement about your estate.