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High

Connection confusion in gRPC

  • Disclosed: 05.07.2023
  • Updated: 11.10.2026 13:20

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.

Affected software

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PlatformPackageVulnerable versionsFixed in
Java / Kotlin (Maven) io.grpc:grpc-protobuf >= 1.53.0, < 1.53.1, >= 1.54.0, < 1.54.2 1.53.1, 1.54.2
Python (PyPI) grpcio >= 1.53.0, < 1.53.1, >= 1.54.0, < 1.54.2 1.53.1, 1.54.2

References

CVSS score 7.4/10
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:H
Weakness (CWE)
CWE-440
Platform
Java / Kotlin (Maven), Python (PyPI)
Package
io.grpc:grpc-protobuf, grpcio
Disclosed
05.07.2023
Updated
11.10.2026 13:20

Sources and licenses

OSV / GitHub Advisory Database - PYSEC-2026-1427 - PyPA Advisory Database; CC BY 4.0

OSV / GitHub Advisory Database - GHSA-cfgp-2977-2fmm - CC BY 4.0

Vulnerability history: grpcio

All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.

Total entries
6
First → latest
04.2017 09.2023
Without a fix
0
Exploited in attacks
0

Severity breakdown

  • High 4
  • Medium 1
  • Unrated 1

Disclosures per year

  1. Denial of Service Vulnerability in gRPC TCP Server (Posix-compatible platforms)
    High · 7.5 CVE-2023-4785 >= 1.55.0, < 1.55.3, >= 1.54.0, < 1.54.3, >= 1.53.0, < 1.53.2 1.55.3, 1.54.3, 1.53.2
  2. Excessive Iteration in gRPC
    High · 7.5 CVE-2023-33953 < 1.53.2, >= 1.54.0, < 1.54.3, >= 1.55.0, < 1.55.2, >= 1.56.0, < 1.56.2 1.53.2, 1.54.3, 1.55.2, 1.56.2
  3. gRPC connection termination issue
    Medium · 5.3 CVE-2023-32732 >= 1.53.0, < 1.53.1, >= 1.54.0, < 1.54.2 1.53.1, 1.54.2
  4. gRPC Reachable Assertion issue
    High · 7.5 CVE-2023-1428 >= 1.51.0, < 1.53.0 1.53.0
  5. Connection confusion in gRPC this entry
    High · 7.4 CVE-2023-32731 >= 1.53.0, < 1.53.1, >= 1.54.0, < 1.54.2 1.53.1, 1.54.2
  6. Google gRPC before 2017-03-29 has an out-of-bounds write caused by a heap-based use-after-free related to the grpc_call_destroy function in core/lib/surface/call.c.
    Unrated CVE-2017-8359 < 1.3.0 1.3.0

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