CVE-2023-32731: 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 al...

Description

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 https://github.com/grpc/grpc/pull/33005 https://github.com/grpc/grpc/pull/33005

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS Probability

0.50%

39.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-440

Affected Software

Vendor	Product	Versions
Grpc	Grpc	>= 1.53.0, < 1.55.0

References

Timeline

Published: Jun 9, 2023
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2023-32731?

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 https://github.com/grpc/grpc/pull/33005 https://github.com/grpc/grpc/pull/33005

How severe is CVE-2023-32731?

CVE-2023-32731 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.50% probability of exploitation in the next 30 days.

How do I fix CVE-2023-32731?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.