How severe is CVE-2026-9678?

CVE-2026-9678 has a CVSS score of 5.9/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2026-9678?

CVE-2026-9678 affects the following packages: undici (npm), undici (npm). Ecosystems affected: npm.

How do I fix CVE-2026-9678?

Update undici to 7.28.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-9678 is resolved across your whole dependency graph.

How do I detect CVE-2026-9678 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-2026-9678 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-2026-9678 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-9678 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-2026-9678?

CVE-2026-9678 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 35th 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-2026-9678?

CVE-2026-9678 is classified as CWE-524 (CWE-524). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-9678 published, and has it been updated?

CVE-2026-9678 was published on June 17, 2026 and was last updated on October 21, 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

MEDIUM severity

CVE-2026-9678 — undici

MEDIUM

CVE-2026-9678 is a medium-severity (CVSS 5.9) CWE-524 vulnerability in undici. A fix is available for undici — see the affected versions and patch details below.

undici vulnerable to cross-user information disclosure via shared cache whitespace bypass

Also known asGHSA-pr7r-676h-xcf6

Published

Jun 17, 2026

Updated

Oct 21, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Oct 23, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

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-2026-9678.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs35th percentile — riskier than 35% of all scored CVEsHighest risk

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

How urgent is this, really

CVE-2026-9678 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 395,249 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.

9Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream

undicinpm

133.5Mdownloads / week

Description

Impact

Undici's cache interceptor incorrectly classifies some responses as cacheable when the upstream Cache-Control header uses whitespace-padded qualified private or no-cache field names such as private=" authorization" or no-cache="\tauthorization". The parser preserves the surrounding whitespace, so later comparisons against the literal authorization field name fail and the response is stored.

In shared-cache mode, this allows a response containing one user's authenticated data to be served from cache to a subsequent caller, including an unauthenticated caller, when both requests resolve to the same cache key.

Affected applications are those that explicitly enable the cache interceptor (interceptors.cache()) in shared mode, forward Authorization headers upstream, and receive cacheable responses with non-canonical qualified private or no-cache directives.

Patches

Upgrade to undici v7.28.0 or v8.5.0.

Workarounds

If upgrade is not immediately possible, disable shared-cache mode for traffic that includes Authorization headers, avoid caching responses to authenticated requests, or add Vary: Authorization upstream.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`undici`	≥ 7.0.0&&< 7.28.0	7.28.0`npm install undici@7.28.0`
📦npm	`undici`	≥ 8.0.0&&< 8.5.0	8.5.0`npm install undici@8.5.0`

Affected Products

1 product · 2 configurations

Application

undicinodejs

≥ 8.0.0 && < 8.5.0

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-2026-9678 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 HatModerate

This Moderate information disclosure flaw in Undici's cache interceptor, when configured in shared-cache mode, allows an unauthenticated attacker to retrieve sensitive authenticated user data. This is due to incorrect parsing of Cache-Control headers containing whitespace-padded field names, leading to cached…

Workaround published by Red Hat

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

Source: Red Hat security advisory for CVE-2026-9678 (CC BY 4.0)

Product	Fixed in	Advisory
Red Hat Enterprise Linux 10	`nodejs24-1:24.18.0-1.el10_2`	RHSA-2026:35841
Red Hat Enterprise Linux 10	`nodejs22-1:22.23.1-2.el10_2`	RHSA-2026:35842
Red Hat Enterprise Linux 8	`nodejs:24-8100020260630152626.6d880403`	RHSA-2026:39868
Red Hat Enterprise Linux 8	`nodejs:22-8100020260703140402.6d880403`	RHSA-2026:41947
Red Hat Enterprise Linux 9	`nodejs:24-9080020260626074955.rhel9`	RHSA-2026:35891
Red Hat Enterprise Linux 9	`nodejs:22-9080020260626075442.rhel9`	RHSA-2026:35892
Red Hat Hardened Images	`nodejs26-main-11.16.0-1.26.3.0.1.2.hum1`	RHSA-2026:22380
Red Hat Hardened Images	`nodejs24-main-11.16.0-1.24.18.0.0.3.hum1`	RHSA-2026:38236

Frequently Asked Questions

## Impact Undici's cache interceptor incorrectly classifies some responses as cacheable when the upstream `Cache-Control` header uses whitespace-padded qualified `private` or `no-cache` field names such as `private=" authorization"` or `no-cache="\tauthorization"`. The parser preserves the surrounding whitespace, so later comparisons against the literal `authorization` field name fail and the response is stored. In shared-cache mode, this allows a response containing one user's authenticated data to be served from cache to a subsequent caller, including an unauthenticated caller, when both r