GHSA-v9p9-hfj2-hcw8 — undici
HIGHGHSA-v9p9-hfj2-hcw8 is a high-severity (CVSS 7.5) CWE-248 vulnerability in undici. A fix is available for undici — see the affected versions and patch details below.
Undici has Unhandled Exception in WebSocket Client Due to Invalid server_max_window_bits Validation
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 GHSA-v9p9-hfj2-hcw8.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-v9p9-hfj2-hcw8 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
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
The undici WebSocket client is vulnerable to a denial-of-service attack due to improper validation of the server_max_window_bits parameter in the permessage-deflate extension. When a WebSocket client connects to a server, it automatically advertises support for permessage-deflate compression. A malicious server can respond with an out-of-range server_max_window_bits value (outside zlib's valid range of 8-15). When the server subsequently sends a compressed frame, the client attempts to create a zlib InflateRaw instance with the invalid windowBits value, causing a synchronous RangeError exception that is not caught, resulting in immediate process termination.
The vulnerability exists because:
- The
isValidClientWindowBits()function only validates that the value contains ASCII digits, not that it falls within the valid range 8-15 - The
createInflateRaw()call is not wrapped in a try-catch block - The resulting exception propagates up through the call stack and crashes the Node.js process
Patches
Has the problem been patched? What versions should users upgrade to?
Workarounds
Is there a way for users to fix or remediate the vulnerability without upgrading?
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | undici | all versions | 6.24.0npm install undici@6.24.0 |
| 📦npm | undici | ≥ 7.0.0&&< 7.24.0 | 7.24.0npm install undici@7.24.0 |
Detection & 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 6.24.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-v9p9-hfj2-hcw8 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.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-v9p9-hfj2-hcw8 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-v9p9-hfj2-hcw8. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
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.
| Product | Fixed in | Advisory |
|---|---|---|
| Cryostat 4 on RHEL 9 | cryostat/cryostat-openshift-console-plugin-rhel9:4.2.0-9 | RHSA-2026:17789 |
| Red Hat Enterprise Linux 10 | nodejs22-1:22.22.2-1.el10_1 | RHSA-2026:7080 |
| Red Hat Enterprise Linux 10 | nodejs24-1:24.14.1-2.el10_1 | RHSA-2026:7675 |
| Red Hat Enterprise Linux 10.0 Extended Update Support | nodejs22-1:22.22.2-2.el10_0 | RHSA-2026:7310 |
| Red Hat Enterprise Linux 8 | nodejs:22-8100020260331102257.6d880403 | RHSA-2026:7123 |
| Red Hat Enterprise Linux 8 | nodejs:24-8100020260408131901.6d880403 | RHSA-2026:7670 |
| Red Hat Enterprise Linux 9 | nodejs:22-9070020260401095228.rhel9 | RHSA-2026:7302 |
| Red Hat Enterprise Linux 9 | nodejs:24-9070020260402152654.rhel9 | RHSA-2026:7350 |
Frequently Asked Questions
Is GHSA-v9p9-hfj2-hcw8 in your dependencies?
O3 Security finds GHSA-v9p9-hfj2-hcw8 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.