How severe is CVE-2026-6734?

CVE-2026-6734 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2026-6734?

CVE-2026-6734 affects the following packages: undici (npm), undici (npm). Ecosystems affected: npm.

How do I fix CVE-2026-6734?

Update undici to 7.28.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-6734 is resolved across your whole dependency graph.

How do I detect CVE-2026-6734 in my npm dependencies?

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

How do I mitigate CVE-2026-6734 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-6734 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-6734 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-2026-6734?

CVE-2026-6734 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 30th 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-2026-6734?

CVE-2026-6734 is classified as CWE-346 (CWE-346), CWE-940 (CWE-940). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-6734 published, and has it been updated?

CVE-2026-6734 was published on June 17, 2026 and was last updated on September 12, 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-2026-6734 — undici

HIGHFix: nodejs/undici#5041

CVE-2026-6734 is a high-severity (CVSS 7.5) CWE-346 vulnerability in undici. A fix is available for undici — see the affected versions and patch details below.

undici vulnerable to cross-origin request routing via SOCKS5 proxy pool reuse

Also known asGHSA-hm92-r4w5-c3mj

Published

Jun 17, 2026

Updated

Sep 12, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Sep 26, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

A successful exploit gives an attacker total control of the affected component, not partial access.
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-2026-6734.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs30th percentile — riskier than 30% of all scored CVEsHighest risk

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

How urgent is this, really

CVE-2026-6734 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 379,842 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

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.

8Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream

undicinpm

211.9Mdownloads / week

Description

Impact

When using Socks5ProxyAgent, undici reuses a single connection pool across different origins without verifying that the pool's origin matches the requested origin. All requests are dispatched through the pool connected to the first origin, regardless of the intended destination.

This causes cross-origin request routing: credentials and request data intended for origin B are sent to origin A, responses from the wrong origin are trusted, and HTTPS requests may be silently downgraded to HTTP.

Impacted users are applications that use Socks5ProxyAgent (directly or via setGlobalDispatcher) and make requests to more than one origin.

This was introduced in undici 7.23.0 via #4385 and affects all versions through 8.1.0.

Patches

Upgrade to undici v7.28.0 or v8.2.0

Workarounds

Use a separate Socks5ProxyAgent instance per origin, or avoid using Socks5ProxyAgent with multiple origins.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`undici`	≥ 7.23.0&&< 7.28.0	7.28.0`npm install undici@7.28.0`
📦npm	`undici`	≥ 8.0.0&&< 8.2.0	8.2.0`npm install undici@8.2.0`

Affected Products

1 product · 2 configurations

Application

undicinodejs

≥ 8.0.0 && < 8.2.0

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for undici, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update undici to 7.28.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-6734 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

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

This is rated as an Important security flaw. The `undici` library, when configured with `Socks5ProxyAgent` to handle requests for multiple origins, incorrectly reuses connection pools. This can lead to sensitive data and credentials being misrouted to unintended destinations, potentially downgrading HTTPS connections…

Workaround published by Red Hat

The single most impactful mitigation is applying network egress controls to restrict which external destinations affected applications can reach. Because the vulnerability causes requests to be misrouted to wrong origins, limiting the set of reachable origins directly reduces the attack surface. These controls collectively limit the blast radius of the connection pool misrouting — the attacker must compromise one of the explicitly allowed destinations rather than any arbitrary origin — but they do not fix the underlying logic bug.

Source: Red Hat security advisory for CVE-2026-6734 (CC BY 4.0)

Product	Fixed in	Advisory
Cryostat 4 on RHEL 9	`cryostat/cryostat-grafana-dashboard-rhel9:4.2.0-13`	RHSA-2026:48151
Red Hat Enterprise Linux 10	`nodejs24-1:24.18.0-1.el10_2`	RHSA-2026:35841
Red Hat Enterprise Linux 8	`nodejs:24-8100020260630152626.6d880403`	RHSA-2026:39868
Red Hat Enterprise Linux 9	`nodejs:24-9080020260626074955.rhel9`	RHSA-2026:35891
Cluster Observability Operator 1.5.0	`cluster-observability-operator/distributed-tracing-console-plugin-pf4-rhel9:1782840519`	RHSA-2026:34342
Red Hat Developer Hub 1.10	`rhdh/rhdh-hub-rhel9:1783448184`	RHSA-2026:36754
Red Hat Developer Hub 1.9	`rhdh/rhdh-hub-rhel9:1784210921`	RHSA-2026:41929
Red Hat Hardened Images	`nodejs26-main-26.3.0-1.2.hum1`	RHSA-2026:22380

Frequently Asked Questions

## Impact When using `Socks5ProxyAgent`, undici reuses a single connection pool across different origins without verifying that the pool's origin matches the requested origin. All requests are dispatched through the pool connected to the first origin, regardless of the intended destination. This causes cross-origin request routing: credentials and request data intended for origin B are sent to origin A, responses from the wrong origin are trusted, and HTTPS requests may be silently downgraded to HTTP. Impacted users are applications that use `Socks5ProxyAgent` (directly or via `setGlobalDis

O3 Security · Impact-Aware SCA

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