When gRPC HTTP2 stack raised a header size exceeded error, it skipped parsing the rest of the HPACK frame. This caused any HPACK table mutations to also be skipped, resulting in a desynchronization of HPACK tables between sender and receiver. If leveraged, say, between a proxy and a backend, this could lead to requests from the proxy being interpreted as containing headers from different proxy clients - leading to an information leak that can be used for privilege escalation or data exfiltration. We recommend upgrading beyond the commit contained in  grpc/grpc#32309

References

• https://nvd.nist.gov/vuln/detail/CVE-2023-32731
• grpc/grpc#32309
• grpc/grpc#33005
• grpc/grpc#33463
• https://github.com/rubysec/ruby-advisory-db/blob/master/gems/grpc/CVE-2023-32731.yml