PYSEC-2026-1427

Vulnerability from pysec - Published: 2026-07-07 11:45 - Updated: 2026-07-07 17:24
VLAI
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.

Severity
7.4 (High)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:H
Impacted products
Name purl
grpcio pkg:pypi/grpcio
Aliases
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "grpcio",
        "purl": "pkg:pypi/grpcio"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.53.0"
            },
            {
              "fixed": "1.53.1"
            },
            {
              "introduced": "1.54.0"
            },
            {
              "fixed": "1.54.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.53.0",
        "1.54.0"
      ]
    }
  ],
  "aliases": [
    "CVE-2023-32731",
    "GHSA-cfgp-2977-2fmm"
  ],
  "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.",
  "id": "PYSEC-2026-1427",
  "modified": "2026-07-07T17:24:16.370772Z",
  "published": "2026-07-07T11:45:19.959086Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2023-32731"
    },
    {
      "type": "WEB",
      "url": "https://github.com/grpc/grpc/issues/33463"
    },
    {
      "type": "WEB",
      "url": "https://github.com/grpc/grpc/pull/32309"
    },
    {
      "type": "WEB",
      "url": "https://github.com/grpc/grpc/pull/33005"
    },
    {
      "type": "WEB",
      "url": "https://github.com/grpc/grpc/commit/29d8beee0ac2555773b2a2dda5601c74a95d6c10"
    },
    {
      "type": "WEB",
      "url": "https://github.com/grpc/grpc/commit/65a2a895afaf1d2072447b9baf246374b182a946"
    },
    {
      "type": "WEB",
      "url": "https://github.com/grpc/grpc/releases/tag/v1.53.1"
    },
    {
      "type": "WEB",
      "url": "https://github.com/grpc/grpc/releases/tag/v1.54.2"
    },
    {
      "type": "WEB",
      "url": "https://github.com/rubysec/ruby-advisory-db/blob/master/gems/grpc/CVE-2023-32731.yml"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/grpcio"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-cfgp-2977-2fmm"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Connection confusion in gRPC"
}



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