# CVE-2023-32731: Information leak in gRPC

> An HPACK desynchronization flaw in gRPC allows attackers to leak headers between clients, potentially enabling data exfiltration or privilege escalation.

- **Severity:** High 7.4 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 9 Jun 2023
- **Updated:** 26 Sep 2024
- **Also known as:** BELL-CVE-2023-32731, GHSA-cfgp-2977-2fmm, PYSEC-2026-1427, UBUNTU-CVE-2023-32731

## What is CVE-2023-32731?

CVE-2023-32731 is a high-severity vulnerability in Google gRPC, published on 9 Jun 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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

Weakness: CWE-440 (Expected Behavior Violation)

## Which versions are affected by CVE-2023-32731?

13 open source packages ship an affected version, including grpcio, io.grpc:grpc-protobuf and grpc. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `grpcio` | PyPI | From 1.53.0 | 1.53.1, 1.54.2 |
| `grpcio` | PyPI | From 1.53.0 | 1.53.1 |
| `grpcio` | PyPI | From 1.53.0 | 1.53.1 |
| `grpcio` | PyPI | From 1.54.0 | 1.54.2 |
| `grpcio` | PyPI | From 1.54.0 | 1.54.2 |
| `io.grpc:grpc-protobuf` | Maven | From 1.53.0 | 1.53.1 |
| `io.grpc:grpc-protobuf` | Maven | From 1.53.0 | 1.53.1 |
| `io.grpc:grpc-protobuf` | Maven | From 1.54.0 | 1.54.2 |
| `io.grpc:grpc-protobuf` | Maven | From 1.54.0 | 1.54.2 |
| `grpc` | RubyGems | From 1.53.0 | 1.53.1 |
| `grpc` | RubyGems | From 1.53.0 | 1.53.1 |
| `grpc` | RubyGems | From 1.54.0 | 1.54.2 |
| `grpc` | RubyGems | From 1.54.0 | 1.54.2 |

Products: Grpc Grpc.

## How do I fix CVE-2023-32731?

Upgrade grpcio to a fixed version for your release line: 1.53.1 or 1.54.2.

## Is CVE-2023-32731 being exploited?

There is no known exploitation of CVE-2023-32731 in the wild and no public exploit code.

## Other vulnerabilities in Google gRPC

- [CVE-2017-9431](https://insights.sbomify.com/CVE-2017-9431/): Memory corruption in n/a (critical 9.8)
- [CVE-2017-8359](https://insights.sbomify.com/CVE-2017-8359/): Use after free in n/a (critical 9.8)
- [CVE-2017-7860](https://insights.sbomify.com/CVE-2017-7860/): Memory corruption in n/a (critical 9.8)
- [CVE-2017-7861](https://insights.sbomify.com/CVE-2017-7861/): Memory corruption in n/a (critical 9.8)
- [CVE-2026-33186](https://insights.sbomify.com/CVE-2026-33186/): gRPC-Go has an authorization bypass via missing leading slash in :path (critical 9.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-32731 and fix it if it is affected.

What it is: CVE-2023-32731 is a high-severity vulnerability in Google gRPC, published on 9 Jun 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2023-32731 in the wild and no public exploit code.

Affected packages and fixed versions:
- grpcio (PyPI): affected from 1.53.0; fixed in 1.53.1, 1.54.2
- grpcio (PyPI): affected from 1.53.0; fixed in 1.53.1
- grpcio (PyPI): affected from 1.53.0; fixed in 1.53.1
- grpcio (PyPI): affected from 1.54.0; fixed in 1.54.2
- grpcio (PyPI): affected from 1.54.0; fixed in 1.54.2
- io.grpc:grpc-protobuf (Maven): affected from 1.53.0; fixed in 1.53.1
- io.grpc:grpc-protobuf (Maven): affected from 1.53.0; fixed in 1.53.1
- io.grpc:grpc-protobuf (Maven): affected from 1.54.0; fixed in 1.54.2
- io.grpc:grpc-protobuf (Maven): affected from 1.54.0; fixed in 1.54.2
- grpc (RubyGems): affected from 1.53.0; fixed in 1.53.1
- grpc (RubyGems): affected from 1.53.0; fixed in 1.53.1
- grpc (RubyGems): affected from 1.54.0; fixed in 1.54.2

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2023-32731/ (Markdown: https://insights.sbomify.com/CVE-2023-32731/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-32731
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-32731
- OSV: https://osv.dev/vulnerability/CVE-2023-32731

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-32731/
Summaries are generated and may contain mistakes; the official description above is the record.