How severe is CVE-2026-6321?

CVE-2026-6321 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2026-6321?

CVE-2026-6321 affects the following packages: fast-uri (npm), fast-uri (npm). Ecosystems affected: npm.

How do I fix CVE-2026-6321?

Update fast-uri to 3.1.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-6321 is resolved across your whole dependency graph.

How do I detect CVE-2026-6321 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for fast-uri, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-6321 if there is no patch (or I can't update yet)?

Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Is CVE-2026-6321 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-6321 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-6321?

CVE-2026-6321 has an EPSS (Exploit Prediction Scoring System) score of 0.6%, placing it in the 51th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-6321?

CVE-2026-6321 is classified as Path Traversal (CWE-22). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2026-6321 published, and has it been updated?

CVE-2026-6321 was published on May 4, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦

📦 npm

Not in CISA KEV

HIGH severity

CVE-2026-6321 — fast-uri

HIGH

CVE-2026-6321 is a high-severity (CVSS 7.5) Path Traversal vulnerability in fast-uri. A fix is available for fast-uri — see the affected versions and patch details below.

fast-uri vulnerable to path traversal via percent-encoded dot segments

Also known asGHSA-q3j6-qgpj-74h6

Published

May 4, 2026

Updated

Oct 28, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Nov 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-6321.

EPSS Exploitation Probability

via FIRST.org ↗

0.6%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs51th percentile — riskier than 51% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

2 pkgs affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

353other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

fast-urinpm

217.7Mdownloads / week

Description

Impact

fast-uri v3.1.0 and earlier decodes percent-encoded path separators (%2F) and dot segments (%2E) before applying dot-segment removal in normalize() and equal(). This makes encoded path data behave like real / and .., so distinct URIs collapse onto the same normalized path.

For example, http://example.com/public/%2e%2e/admin normalizes to http://example.com/admin, and equal() considers them the same URI.

Applications that normalize or compare attacker-controlled URLs to enforce path-based policy can be bypassed. A path that looks confined under an allowed prefix can normalize to a different location.

Patches

Upgrade to fast-uri >= 3.1.1, or if you are in the v2.x release line, v2.4.1

Workarounds

None. Upgrade to the patched version.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`fast-uri`	≥ 3.0.0&&< 3.1.1	3.1.1`npm install fast-uri@3.1.1`
📦npm	`fast-uri`	all versions	2.4.1`npm install fast-uri@2.4.1`

Affected Products

1 product · 1 configurations

Application

fast-uriopenjsf

< 3.1.1

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for fast-uri, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update fast-uri to 3.1.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-6321 is resolved across your whole dependency graph.
Workarounds
Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

Product	Fixed in	Advisory
HawtIO HawtIO 4.4.0	`io.hawt-project`	RHSA-2026:25089
Red Hat Ansible Automation Platform 2.5 for RHEL 8	`automation-gateway-0:2.5.20260715-1.el8ap`	RHSA-2026:42078
Red Hat Ansible Automation Platform 2.6 for RHEL 9	`automation-platform-ui-0:2.6.11-1.el9ap`	RHSA-2026:42079
Red Hat Enterprise Linux 10	`rh-podman-desktop-0:1.1.1-1.el10_2`	RHSA-2026:37385
Cluster Observability Operator 1.5	`cluster-observability-operator/distributed-tracing-console-plugin-pf4-rhel9:1782840519`	RHSA-2026:34342
Network Observability (NETOBSERV) 1.12.3	`network-observability/network-observability-console-plugin-rhel9:1780556069`	RHSA-2026:24473
Red Hat Ansible Automation Platform 2.5	`ansible-automation-platform-25/lightspeed-rhel8:1780082949`	RHSA-2026:24766
Red Hat Ansible Automation Platform 2.6	`ansible-automation-platform-26/lightspeed-rhel9:1779784904`	RHSA-2026:24866

Frequently Asked Questions

### Impact `fast-uri` v3.1.0 and earlier decodes percent-encoded path separators (`%2F`) and dot segments (`%2E`) before applying dot-segment removal in `normalize()` and `equal()`. This makes encoded path data behave like real `/` and `..`, so distinct URIs collapse onto the same normalized path. For example, `http://example.com/public/%2e%2e/admin` normalizes to `http://example.com/admin`, and `equal()` considers them the same URI. Applications that normalize or compare attacker-controlled URLs to enforce path-based policy can be bypassed. A path that looks confined under an allowed prefi

O3 Security · Impact-Aware SCA

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