FKIE_CVE-2026-73548

Vulnerability from fkie_nvd - Published: 2026-09-21 20:17 - Updated: 2026-09-21 20:17
Severity
7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Summary
Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.36.10, 1.37.6, 1.38.4, and 1.39.1, Envoy forwards data for a configured non-WebSocket HTTP upgrade before the upstream accepts the upgrade. An unauthenticated HTTP/2 client can place a complete HTTP/1.1 request in extended CONNECT data; Envoy downgrades the request, writes the data unframed to a keep-alive HTTP/1.1 upstream, and returns the socket to the shared pool while the smuggled response remains queued. A different downstream client can then receive the attacker's response. The relevant scope boundary is that webSocket upgrades, plain CONNECT, disabled backend keep-alive, per-downstream pools, and max_requests_per_connection set to 1 are not affected by the demonstrated path. This issue is fixed in versions 1.36.10, 1.37.6, 1.38.4, and 1.39.1.
References
security-advisories@github.comhttps://github.com/envoyproxy/envoy/commit/309855626966cff176155c821043ed3b44671361
security-advisories@github.comhttps://github.com/envoyproxy/envoy/commit/3c7998545a9c9fb3933a4bc1907d92f0e752bc2b
security-advisories@github.comhttps://github.com/envoyproxy/envoy/commit/4633b8cce3d15b8734eefe232e30c12b0140b91c
security-advisories@github.comhttps://github.com/envoyproxy/envoy/commit/bd6711f2617658e28dfa3df3dace6bfe3cfc0766
security-advisories@github.comhttps://github.com/envoyproxy/envoy/releases/tag/v1.36.10
security-advisories@github.comhttps://github.com/envoyproxy/envoy/releases/tag/v1.37.6
security-advisories@github.comhttps://github.com/envoyproxy/envoy/releases/tag/v1.38.4
security-advisories@github.comhttps://github.com/envoyproxy/envoy/releases/tag/v1.39.1
security-advisories@github.comhttps://github.com/envoyproxy/envoy/security/advisories/GHSA-3vhp-c83q-jqc2
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "envoy",
          "vendor": "envoyproxy",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 1.36.10"
            },
            {
              "status": "affected",
              "version": "\u003e= 1.37.0, \u003c 1.37.6"
            },
            {
              "status": "affected",
              "version": "\u003e= 1.38.0, \u003c 1.38.4"
            },
            {
              "status": "affected",
              "version": "\u003e= 1.39.0, \u003c 1.39.1"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.36.10, 1.37.6, 1.38.4, and 1.39.1, Envoy forwards data for a configured non-WebSocket HTTP upgrade before the upstream accepts the upgrade. An unauthenticated HTTP/2 client can place a complete HTTP/1.1 request in extended CONNECT data; Envoy downgrades the request, writes the data unframed to a keep-alive HTTP/1.1 upstream, and returns the socket to the shared pool while the smuggled response remains queued. A different downstream client can then receive the attacker\u0027s response. The relevant scope boundary is that webSocket upgrades, plain CONNECT, disabled backend keep-alive, per-downstream pools, and max_requests_per_connection set to 1 are not affected by the demonstrated path. This issue is fixed in versions 1.36.10, 1.37.6, 1.38.4, and 1.39.1."
    }
  ],
  "id": "CVE-2026-73548",
  "lastModified": "2026-09-21T20:17:28.397",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-09-21T20:17:28.397",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/envoyproxy/envoy/commit/309855626966cff176155c821043ed3b44671361"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/envoyproxy/envoy/commit/3c7998545a9c9fb3933a4bc1907d92f0e752bc2b"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/envoyproxy/envoy/commit/4633b8cce3d15b8734eefe232e30c12b0140b91c"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/envoyproxy/envoy/commit/bd6711f2617658e28dfa3df3dace6bfe3cfc0766"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/envoyproxy/envoy/releases/tag/v1.36.10"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/envoyproxy/envoy/releases/tag/v1.37.6"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/envoyproxy/envoy/releases/tag/v1.38.4"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/envoyproxy/envoy/releases/tag/v1.39.1"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/envoyproxy/envoy/security/advisories/GHSA-3vhp-c83q-jqc2"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-444"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
    }
  ]
}



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