{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/envoyproxy/envoy"
      },
      "versions": [
        "1.37.0"
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/envoyproxy/envoy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.36.0"
            },
            {
              "last_affected": "1.36.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/envoyproxy/envoy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.35.0"
            },
            {
              "last_affected": "1.35.8"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/envoyproxy/envoy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "1.34.12"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-26311"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-416"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-10T18:31:23Z",
    "nvd_published_at": "2026-03-10T20:16:36Z",
    "severity": "MODERATE"
  },
  "details": "**Note:**\nThis vulnerability was originally reported to the Google OSS VRP (Issue ID: [477542544](https://issuetracker.google.com/issues/477542544)). The Google Security Team requested that I coordinate directly with the Envoy maintainers for triage and remediation. I am submitting this report here to facilitate that process.\n\n**Technical Details**\nI have identified a logic vulnerability in Envoy\u0027s HTTP connection manager (`FilterManager`) that allows for **Zombie Stream Filter Execution**. This issue creates a \"Use-After-Free\" (UAF) or state-corruption window where filter callbacks are invoked on an HTTP stream that has already been logically reset and cleaned up.\n\n**Mechanism:**\nThe vulnerability resides in `source/common/http/filter_manager.cc` within the `FilterManager::decodeData` method.\n\nWhen an HTTP/2 stream encounters a reset condition (e.g., `StreamIdleTimeout`, `OverloadManager` limits, or a local reset triggered by a filter), Envoy calls `onResetStream`. This method:\n1.  Sets the internal state `state_.saw_downstream_reset_ = true`.\n2.  Invokes `onDestroy()` on all filters in the chain (allowing them to release resources/pointers).\n3.  Schedules the `ActiveStream` object for **deferred deletion** (cleanup happens later in the event loop).\n\n**The Flaw:**\nThe `ActiveStream` object remains valid in memory during the deferred deletion window. If a `DATA` frame arrives on this stream immediately after the reset (e.g., in the same packet processing cycle), the HTTP/2 codec invokes `ActiveStream::decodeData`, which cascades to `FilterManager::decodeData`.\n\n`FilterManager::decodeData` **fails to check the `saw_downstream_reset_` flag**. It iterates over the `decoder_filters_` list and invokes `decodeData()` on filters that have already received `onDestroy()`.\n\n**Root Cause Code Location:**\nFile: `source/common/http/filter_manager.cc`\nFunction: `FilterManager::decodeData`\n\n```cpp\nvoid FilterManager::decodeData(...) {\n  if (stopDecoderFilterChain()) { return; }\n\n  // Vulnerability: Missing check for state_.saw_downstream_reset_\n  // Execution proceeds into the loop even if the stream is logically dead.\n\n  auto trailers_added_entry = decoder_filters_.end();\n  for (; entry != decoder_filters_.end(); entry++) {\n      // ... calls (*entry)-\u003ehandle_-\u003edecodeData(data) on destroyed filters ...\n  }\n}\n```\n\n**Suggested Fix:**\nAdd an explicit state check at the beginning of `FilterManager::decodeData`.\n\n```cpp\n// Prevent execution on streams that have been reset but not yet destroyed.\nif (state_.saw_downstream_reset_) {\n  return;\n}\n```\n\n---\n\n## Impact Analysis\n\n**Who can exploit this:**\nAny remote attacker capable of establishing an HTTP/2 or HTTP/3 connection. No privileges/authentication required.\n\n**Impact \u0026 Gain:**\n**1. Memory Corruption \u0026 Potential Remote Code Execution:**\nWhile the immediate symptom is a crash (DoS), the underlying primitive is a **Use-After-Free (CWE-416)**.\n* **Mechanism:** When `onDestroy()` is called on filters (e.g., Lua, Wasm, or complex native filters), they release internal structures and invalidate pointers.\n* **Exploitation:** By forcing `decodeData()` to execute on these now-freed objects, an attacker triggers undefined behavior. In a heap-groomed environment, an attacker could potentially replace the freed filter object with a malicious payload before the \"Zombie\" `decodeData` call occurs. This would allow for vtable hijacking or arbitrary write-what-where primitives, leading to **Remote Code Execution (RCE)**.\n* **Risk Amplification:** This is particularly dangerous for Envoy deployments using memory-unsafe extensions or third-party filters (C++ extensions), where `onDestroy` logic is relied upon for safety.\n\n**2. Security Control Bypass:**\nThe vulnerability defeats Envoy\u0027s \"Fail-Closed\" security architecture.\n* **Scenario:** If a stream is reset due to a security violation (e.g., `StreamIdleTimeout`, `OverloadManager` rejection, or WAF triggering), this vulnerability allows the attacker to **bypass the termination**.\n* **Result:** The attacker can force the processing of \"Data\" frames on a connection that the security policy explicitly attempted to close, allowing malicious payloads to reach deeper into the filter chain or backend services despite the rejection.\n\n---\n\n## Proof of Concept (Unit Test)\n\n**Description:**\nThe attached C++ unit test (`zombie_stream_poc_test.cc`) deterministically reproduces the vulnerability. It creates a stream, manually triggers a reset (simulating an Overload), and then immediately injects a DATA frame. The test asserts that the filter\u0027s `decodeData` callback is invoked on the reset stream.\n\n```cpp\n#include \"test/common/http/conn_manager_impl_test_base.h\"\n#include \"gmock/gmock.h\"\n#include \"gtest/gtest.h\"\n\nusing testing::_;\nusing testing::Invoke;\nusing testing::NiceMock;\nusing testing::Return;\n\nnamespace Envoy {\nnamespace Http {\n\n/**\n * Proof of Concept for \"Zombie Stream Filter Execution\" (HTTP/2 Reset Re-entrancy)\n * * Logic flow:\n * 1. Open a stream with HEADERS.\n * 2. Force a stream reset (simulating an Overload or Timeout).\n * 3. Immediately inject DATA into the stream.\n * 4. ASSERT that the filter\u0027s decodeData is called despite the stream being reset.\n */\nclass ZombieStreamPocTest : public HttpConnectionManagerImplTest {\n};\n\nTEST_F(ZombieStreamPocTest, ReproducedZombieFilterExecution) {\n  setup(SetupOpts().setTracing(false));\n\n  // 1. Setup a mock filter\n  std::shared_ptr\u003cMockStreamDecoderFilter\u003e filter(new NiceMock\u003cMockStreamDecoderFilter\u003e());\n   \n  // Vuln confirmation:\n  // We expect decodeData to be called on this filter even though the stream is reset.\n  // In a secure/patched implementation, this EXPECT_CALL should fail (Times(0)).\n  EXPECT_CALL(*filter, decodeData(_, _))\n      .Times(1)\n      .WillOnce(Invoke([\u0026](Buffer::Instance\u0026, bool) -\u003e FilterDataStatus {\n          ENVOY_LOG_MISC(error, \"!!! VULNERABILITY REPRODUCED: decodeData called on a reset stream !!!\");\n          return FilterDataStatus::Continue;\n      }));\n\n  EXPECT_CALL(*filter, decodeHeaders(_, false))\n      .WillOnce(Return(FilterHeadersStatus::StopIteration));\n\n  // Register the filter\n  EXPECT_CALL(filter_factory_, createFilterChain(_))\n      .WillOnce(Invoke([\u0026](FilterChainFactoryCallbacks\u0026 callbacks) -\u003e bool {\n        auto factory = createDecoderFilterFactoryCb(filter);\n        callbacks.setFilterConfigName(\"vulnerable_filter\");\n        factory(callbacks);\n        return true;\n      }));\n\n  // 2. Start the stream\n  EXPECT_CALL(*codec_, dispatch(_))\n      .WillOnce(Invoke([\u0026](Buffer::Instance\u0026) -\u003e Http::Status {\n        decoder_ = \u0026conn_manager_-\u003enewStream(response_encoder_);\n        RequestHeaderMapPtr headers{new TestRequestHeaderMapImpl{\n            {\":authority\", \"host\"}, {\":path\", \"/\"}, {\":method\", \"POST\"}}};\n        decoder_-\u003edecodeHeaders(std::move(headers), false);\n        return Http::okStatus();\n      }));\n\n  // Dispatch headers\n  Buffer::OwnedImpl header_buffer(\"headers\");\n  conn_manager_-\u003eonData(header_buffer, false);\n\n  // 3. Trigger a Reset on the ActiveStream\n  // This simulates Envoy terminating the stream due to an external event (Overload, Timeout).\n  auto* active_stream = dynamic_cast\u003cConnectionManagerImpl::ActiveStream*\u003e(decoder_);\n  \n  // This sets state_.saw_downstream_reset_ = true and triggers filter-\u003eonDestroy()\n  active_stream-\u003eonResetStream(StreamResetReason::LocalReset, \"simulated_overload\");\n\n  // 4. Attack: Send DATA to the \"Zombie\" stream\n  // The ActiveStream object is still alive in the deferred delete list.\n  Buffer::OwnedImpl malicious_payload(\"attacker_data\");\n   \n  // This call reaches the filter because FilterManager::decodeData misses the check!\n  active_stream-\u003edecodeData(malicious_payload, false);\n}\n\n} // namespace Http\n} // namespace Envoy\n```",
  "id": "GHSA-84xm-r438-86px",
  "modified": "2026-03-10T22:54:46Z",
  "published": "2026-03-10T18:31:23Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/envoyproxy/envoy/security/advisories/GHSA-84xm-r438-86px"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-26311"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/envoyproxy/envoy"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Envoy: HTTP - filter chain execution on reset streams causing UAF crash"
}

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              "criteria": "cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*",
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  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Envoy is a high-performance edge/middle/service proxy. Prior to 1.37.1, 1.36.5, 1.35.8, and 1.34.13, a logic vulnerability in Envoy\u0027s HTTP connection manager (FilterManager) that allows for Zombie Stream Filter Execution. This issue creates a \"Use-After-Free\" (UAF) or state-corruption window where filter callbacks are invoked on an HTTP stream that has already been logically reset and cleaned up. The vulnerability resides in source/common/http/filter_manager.cc within the FilterManager::decodeData method. The ActiveStream object remains valid in memory during the deferred deletion window. If a DATA frame arrives on this stream immediately after the reset (e.g., in the same packet processing cycle), the HTTP/2 codec invokes ActiveStream::decodeData, which cascades to FilterManager::decodeData. FilterManager::decodeData fails to check the saw_downstream_reset_ flag. It iterates over the decoder_filters_ list and invokes decodeData() on filters that have already received onDestroy(). This vulnerability is fixed in 1.37.1, 1.36.5, 1.35.8, and 1.34.13."
    },
    {
      "lang": "es",
      "value": "Envoy es un proxy de borde/intermedio/servicio de alto rendimiento. Antes de 1.37.1, 1.36.5, 1.35.8 y 1.34.13, una vulnerabilidad l\u00f3gica en el gestor de conexiones HTTP de Envoy (FilterManager) permite la Ejecuci\u00f3n de Filtro de Flujo Zombie. Este problema crea una ventana de \u0027Uso despu\u00e9s de liberaci\u00f3n\u0027 (UAF) o de corrupci\u00f3n de estado donde las devoluciones de llamada de filtro se invocan en un flujo HTTP que ya ha sido l\u00f3gicamente restablecido y limpiado. La vulnerabilidad reside en source/common/http/filter_manager.cc dentro del m\u00e9todo FilterManager::decodeData. El objeto ActiveStream permanece v\u00e1lido en memoria durante la ventana de eliminaci\u00f3n diferida. Si un frame DATA llega en este flujo inmediatamente despu\u00e9s del restablecimiento (por ejemplo, en el mismo ciclo de procesamiento de paquetes), el c\u00f3dec HTTP/2 invoca ActiveStream::decodeData, lo que se propaga a FilterManager::decodeData. FilterManager::decodeData no verifica el flag saw_downstream_reset_. Itera sobre la lista decoder_filters_ e invoca decodeData() en filtros que ya han recibido onDestroy(). Esta vulnerabilidad se corrige en 1.37.1, 1.36.5, 1.35.8 y 1.34.13."
    }
  ],
  "id": "CVE-2026-26311",
  "lastModified": "2026-03-11T16:03:58.183",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "HIGH",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 5.9,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
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        "exploitabilityScore": 2.2,
        "impactScore": 3.6,
        "source": "security-advisories@github.com",
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  "published": "2026-03-10T20:16:36.183",
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      "source": "security-advisories@github.com",
      "tags": [
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        "Mitigation",
        "Vendor Advisory"
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      "url": "https://github.com/envoyproxy/envoy/security/advisories/GHSA-84xm-r438-86px"
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  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
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          "lang": "en",
          "value": "CWE-416"
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      "source": "security-advisories@github.com",
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}