CVE-2022-21671 is a high-severity (CVSS 8.1) Information Exposure vulnerability in @replit/crosis. O3 Security confirms whether CVE-2022-21671 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Potential exposure of Replit tokens to an Unauthorized Actor in @replit/crosis
Real-World Exposure
@replit/crosisReal-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
@replit/crosis is a JavaScript client that speaks Replit's container protocol. A vulnerability that involves exposure of sensitive information exists in versions prior to 7.3.1. When using this library as a way to programmatically communicate with Replit in a standalone fashion, if there are multiple failed attempts to contact Replit through a WebSocket, the library will attempt to communicate using a fallback poll-based proxy. The URL of the proxy has changed, so any communication done to the previous URL could potentially reach a server that is outside of Replit's control and the token used to connect to the Repl could be obtained by an attacker, leading to full compromise of that Repl (not of the account). This was patched in version 7.3.1 by updating the address of the fallback WebSocket polling proxy to the new one. As a workaround, a user may specify the new address for the polling host (gp-v2.replit.com) in the ConnectArgs. More information about this workaround is available in the GitHub Security Advisory.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @replit/crosis | all versions | 7.3.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @replit/crosis. 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 @replit/crosis to 7.3.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2022-21671 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 CVE-2022-21671 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 CVE-2022-21671. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2022-21671 in your dependencies?
O3 detects CVE-2022-21671 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.