GHSA-g9mf-h72j-4rw9
MEDIUMGHSA-g9mf-h72j-4rw9 is a medium-severity (CVSS 5.9) CWE-770 vulnerability in undici. O3 Security confirms whether GHSA-g9mf-h72j-4rw9 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Undici has an unbounded decompression chain in HTTP responses on Node.js Fetch API via Content-Encoding leads to resource exhaustion
Blast Radius
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
undicinpmDescription
Impact
The fetch() API supports chained HTTP encoding algorithms for response content according to RFC 9110 (e.g., Content-Encoding: gzip, br). This is also supported by the undici decompress interceptor.
However, the number of links in the decompression chain is unbounded and the default maxHeaderSize allows a malicious server to insert thousands compression steps leading to high CPU usage and excessive memory allocation.
Patches
Upgrade to 7.18.2 or 6.23.0.
Workarounds
It is possible to apply an undici interceptor and filter long Content-Encoding sequences manually.
References
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | undici | ≥ 7.0.0&&< 7.18.2 | 7.18.2 |
| 📦npm | undici | all versions | 6.23.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for undici. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update undici to 7.18.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-g9mf-h72j-4rw9 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 pinpoints whether GHSA-g9mf-h72j-4rw9 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-g9mf-h72j-4rw9. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-g9mf-h72j-4rw9 in your dependencies?
O3 detects GHSA-g9mf-h72j-4rw9 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.