CVE-2018-20840

Severity: high (CVSS 8.6 v3.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2019-05-30 · updated 2026-06-17
Weakness: CWE-754

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.

Affected products

Google Api C++ Client: before 2019-04-10 — fixed in 2019-04-10

How to fix

Upgrade to a fixed version: Google Api C++ Client 2019-04-10. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2018-20840 or the next vulnerability affects your stack