GHSA-8xcm-r25x-g524
MEDIUMGHSA-8xcm-r25x-g524 is a medium-severity (CVSS 4.8) CWE-444 vulnerability in undici. O3 Security confirms whether GHSA-8xcm-r25x-g524 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
undici vulnerable to downstream response desynchronization via retry interceptor
Blast Radius
undici📦undici📦undiciReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.
Description
Impact
Undici's interceptors.retry() can deliver a response whose body length does not match the Content-Length header exposed to the application after a retry or resume of a partial response. Applications that use interceptors.retry() and forward upstream response headers and bodies downstream, for example proxy or gateway applications, may emit an invalid HTTP response with a stale Content-Length header. This can lead to downstream response desynchronization, connection hangs, or response corruption in clients or intermediaries that rely on the forwarded framing metadata.
A malicious or faulty upstream can respond to a range request with a 206 Partial Content response such as:
Content-Range: bytes 0-99/300
Content-Length: 300
and then send only 99 bytes before closing the socket. interceptors.retry() can then retry with Range: bytes=99-99, receive the final byte, and deliver a 100-byte body to the application while the response headers still contain Content-Length: 300 from the first response.
The bug requires interceptors.retry() to be enabled, an upstream that returns a partial response with a mismatched framing header, and a downstream forwarder that does not remove or recalculate Content-Length.
Patches
Patched in undici v6.28.0, v7.29.0, and v8.9.0. Users should upgrade to one of these versions or later.
Workarounds
- Disable
interceptors.retry()for untrusted upstreams. - Remove or recalculate
Content-Lengthbefore forwarding a response body assembled or transformed by Undici.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | undici | all versions | 6.28.0 |
| 📦npm | undici | ≥ 7.0.0&&< 7.29.0 | 7.29.0 |
| 📦npm | undici | ≥ 8.0.0&&< 8.9.0 | 8.9.0 |
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 6.28.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-8xcm-r25x-g524 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-8xcm-r25x-g524 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-8xcm-r25x-g524. 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-8xcm-r25x-g524 in your dependencies?
O3 detects GHSA-8xcm-r25x-g524 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.