CVE-2026-84947 is a low-severity (CVSS 3.7) Improper Input Validation vulnerability in undici. A fix is available for undici — see the affected versions and patch details below.
undici vulnerable to response truncation via oversized chunked responses in the dump interceptor
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-2026-84947.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-84947 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 394,803 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
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.
undicinpmDescription
Impact
undici's interceptors.dump() reads and discards response bodies up to a configurable maxSize. When a response declares a Content-Length that exceeds maxSize, the request is aborted cleanly. When a response is sent chunked (no Content-Length) and its body exceeds maxSize, it is not aborted: the interceptor ends the response early once the accumulated size reaches maxSize, and continued delivery from the parser triggers an internal assertion that is caught and turned into a request abort and connection tear-down. The application observes a misleading 200 with an empty or truncated body while the connection is disconnected. Any application using the dump interceptor against untrusted or misbehaving upstreams is affected.
Patches
Upgrade to 7.29.1 or 8.10.2. The dump interceptor now enforces maxSize on both the declared and the received body size, aborting the request with a RequestAbortedError instead of returning a truncated response.
Workarounds
None. Avoid using interceptors.dump() with untrusted upstreams until upgraded.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | undici | ≥ 7.1.0&&< 7.29.1 | 7.29.1npm install undici@7.29.1 |
| 📦npm | undici | ≥ 8.0.0&&< 8.10.2 | 8.10.2npm install undici@8.10.2 |
Affected Products
undicinodejsDetection & mitigation playbook
Open-source dependencyDetect
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 7.29.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-84947 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.
Moderate impact: A flaw in the undici library's dump interceptor can cause applications to terminate connections and receive truncated data when processing oversized chunked HTTP responses without a Content-Length header. This can lead to application instability and incomplete data handling in Red Hat products that…
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-2026-84947 (CC BY 4.0)
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Hardened Images | nodejs26-main-11.19.0-1.26.7.0.1.5.2.hum1 | RHSA-2026:54389 |
| Red Hat Hardened Images | nodejs24-main-11.16.0-1.24.18.1.0.2.2.hum1 | RHSA-2026:54438 |
| Red Hat Hardened Images | grafana12-4-main-12.4.10-0.2.hum1 | RHSA-2026:66008 |
Frequently Asked Questions
Is CVE-2026-84947 in your dependencies?
Find it across npm, including transitive dependencies.