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HIGH7.4

PYSEC-2026-1427

Connection confusion in gRPC

Quick fix

PYSEC-2026-1427 — grpcio: upgrade to the fixed version with the command below.

pip install --upgrade 'grpcio>=1.53.1'

Details

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.

Are you affected?

Enter the version of the package you're using.

Affected packages

PyPI/grpcio
Introduced in: 1.53.0Fixed in: 1.53.1
Fixpip install --upgrade 'grpcio>=1.53.1'

References