Vulnerability-Lookup

CVE-2026-53522 (GCVE-0-2026-53522)

Vulnerability from cvelistv5 – Published: 2026-06-12 21:04 – Updated: 2026-06-15 19:27

Title

Nezha Monitoring: Unbounded WebSocket Streams — Resource Exhaustion DoS

Summary

Nezha Monitoring is a self-hostable, lightweight, servers and websites monitoring and O&M tool. From version 1.0.0 to before version 2.2.0, the Nezha dashboard exposes two endpoints that create long-lived WebSocket streams to monitored agents: POST /api/v1/terminal → createTerminal() (terminal.go:27-67) and POST /api/v1/file → createFM() (fm.go:28-67). Both call rpc.NezhaHandlerSingleton.CreateStream(streamId, ...) which inserts a new ioStreamContext into an unbounded map[string]*ioStreamContext (s.ioStreams in io_stream.go:59-67). There is no per-user rate limit, no global semaphore, and no per-server connection cap. This issue has been patched in version 2.2.0.

Severity

6.5 (Medium)


                        
                          CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-06-15 17:03 UTC

CWE

CWE-770 - Allocation of Resources Without Limits or Throttling

Assigner

GitHub_M mitre root

References

1 reference

URL	Tags
https://github.com/nezhahq/nezha/security/advisor…	x_refsource_CONFIRM

Impacted products

1 product

Vendor	Product	Version	CPE status
nezhahq	nezha	Affected: >= 1.0.0, < 2.2.0	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-53522

Vulnerability from fkie_nvd - Published: 2026-06-12 22:16 - Updated: 2026-06-17 10:57

Severity

6.5 (Medium) - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/nezhahq/nezha/security/advisories/GHSA-jg62-j5h6-8mpq
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/nezhahq/nezha/security/advisories/GHSA-jg62-j5h6-8mpq

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "nezha",
          "vendor": "nezhahq",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 1.0.0, \u003c 2.2.0"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
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    {
      "lang": "en",
      "value": "Nezha Monitoring is a self-hostable, lightweight, servers and websites monitoring and O\u0026M tool. From version 1.0.0 to before version 2.2.0, the Nezha dashboard exposes two endpoints that create long-lived WebSocket streams to monitored agents: POST /api/v1/terminal \u2192 createTerminal() (terminal.go:27-67) and POST /api/v1/file \u2192 createFM() (fm.go:28-67). Both call rpc.NezhaHandlerSingleton.CreateStream(streamId, ...) which inserts a new ioStreamContext into an unbounded map[string]*ioStreamContext (s.ioStreams in io_stream.go:59-67). There is no per-user rate limit, no global semaphore, and no per-server connection cap. This issue has been patched in version 2.2.0."
    }
  ],
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  "lastModified": "2026-06-17T10:57:57.747",
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GHSA-JG62-J5H6-8MPQ

Vulnerability from github – Published: 2026-06-26 23:04 – Updated: 2026-06-26 23:04

Summary

Nezha Monitoring: Unbounded WebSocket Streams — Resource Exhaustion DoS

Details

1. Description

The Nezha dashboard exposes two endpoints that create long-lived WebSocket streams to monitored agents:

POST /api/v1/terminal → createTerminal() (terminal.go:27-67)
POST /api/v1/file → createFM() (fm.go:28-67)

Both call rpc.NezhaHandlerSingleton.CreateStream(streamId, ...) which inserts a new ioStreamContext into an unbounded map[string]*ioStreamContext (s.ioStreams in io_stream.go:59-67). There is no per-user rate limit, no global semaphore, and no per-server connection cap. Each stream allocates:

A ioStreamContext struct with several channels and sync primitives
Two goroutines via StartStream() (io_stream.go:358-369) — bidirectional io.CopyBuffer
A gRPC IOStream between the dashboard and the agent
An agent-side PTY/shell process

Vulnerable code:

terminal.go:27-67 — createTerminal:

func createTerminal(c *gin.Context) (*model.CreateTerminalResponse, error) {
    // ... validation ...
    rpc.NezhaHandlerSingleton.CreateStream(streamId, getUid(c), server.ID)
    // ... sends TaskTypeTerminalGRPC to agent ...
    return &model.CreateTerminalResponse{...}, nil
}

fm.go:28-67 — createFM:

func createFM(c *gin.Context) (*model.CreateFMResponse, error) {
    // ... validation ...
    rpc.NezhaHandlerSingleton.CreateStream(streamId, getUid(c), server.ID)
    // ... sends TaskTypeFM to agent ...
    return &model.CreateFMResponse{...}, nil
}

io_stream.go:55-67 — CreateStreamWithPurpose (inserts into unbounded map):

func (s *NezhaHandler) CreateStreamWithPurpose(...) {
    s.ioStreamMutex.Lock()
    defer s.ioStreamMutex.Unlock()
    s.ioStreams[streamId] = &ioStreamContext{
        creatorUserID:  creatorUserID,
        targetServerID: targetServerID,
        purpose:        purpose,
        userIoConnectCh:  make(chan struct{}),
        agentIoConnectCh: make(chan struct{}),
        revokedCh:        make(chan struct{}),
    }
}

io_stream.go:319-372 — StartStream spawns two goroutines per stream:

func (s *NezhaHandler) StartStream(streamId string, timeout time.Duration) error {
    // ...
    go func() {
        _, innerErr := io.CopyBuffer(userIo, agentIo, bp.buf)
        errCh <- innerErr
    }()
    go func() {
        _, innerErr := io.CopyBuffer(agentIo, userIo, bp.buf)
        errCh <- innerErr
    }()
    return <-errCh
}

The NezhaHandler.ioStreams map is initialized as a plain make(map[string]*ioStreamContext) in nezha.go:36 — no capacity limit, no eviction policy beyond explicit CloseStream / RevokeStreamsForServer.

The HasPermission check at terminal.go:41-43 and fm.go:43-45 controls access scope but does not limit creation volume. A user with ScopeServerExec (terminal) or ScopeServerRead+Write+Delete (file manager) can open unlimited streams.

2. PoC

A conceptual attack (no Docker needed):

# As an authenticated user with a valid JWT or PAT:
for i in {1..1000}; do
  curl -X POST "https://dashboard.example.com/api/v1/terminal" \
    -H "Authorization: Bearer $JWT" \
    -H "Content-Type: application/json" \
    -d '{"server_id": 1}' &
done
wait

Each request: - Creates a new stream entry in ioStreams - Sends a TaskTypeTerminalGRPC task to the agent - When the WebSocket attachment occurs (GET /ws/terminal/{id}), spawns 2 goroutines for I/O relay and allocates a 1 MB buffer per goroutine

The attack targets three resource domains: 1. Dashboard memory/goroutines — each stream adds goroutines, channels, and buffers 2. Agent resources — each stream spawns a PTY/shell process on the monitored server 3. gRPC connection pool — concurrent IOStreams consume gRPC multiplexing capacity

The POST /file (createFM) endpoint provides an alternative path with the same unbounded behavior, using ScopeServerRead+Write+Delete instead of ScopeServerExec.

3. Impact

Denial of Service against the dashboard: memory exhaustion, goroutine starvation, or gRPC stream table overflow from rapid stream creation
Denial of Service against monitored agents: each terminal session spawns a PTY process on the agent — an attacker can crash or degrade all agents behind the dashboard
Operational cascade: if the dashboard OOMs, all agent monitoring and alerting is lost
PAT connection-registry bypass: rapid create-connect-disconnect cycles may evade cleanup tracking

The attack requires only authenticated access with standard scopes — no special privileges. Any team member with terminal access to a server can DoS the entire infrastructure.

4. Remediation

Implement layered rate limiting and concurrency control:

Per-user stream cap in CreateStream — reject if the user already has N active streams (e.g., 10 per user): go func (s *NezhaHandler) CreateStreamWithPurpose(...) { s.ioStreamMutex.Lock() defer s.ioStreamMutex.Unlock() count := 0 for _, ctx := range s.ioStreams { if ctx.creatorUserID == creatorUserID { count++ } } if count >= maxStreamsPerUser { return error } // ... existing code ... }
Per-server semaphore — limit concurrent streams to any single server (e.g., 20 per server)
Rate limiter on createTerminal and createFM — mirror the existing MCP rate limiter (mcp_ratelimit.go) for legacy WebSocket endpoints
Add a configurable MaxStreamsPerUser / MaxStreamsPerServer setting so operators can tune limits without code changes

Severity

6.5 (Medium)


                  
                    CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/nezhahq/nezha"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.0.0"
            },
            {
              "fixed": "2.2.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-53522"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-26T23:04:18Z",
    "nvd_published_at": "2026-06-12T22:16:52Z",
    "severity": "MODERATE"
  },
  "details": "## 1. Description\n\nThe Nezha dashboard exposes two endpoints that create long-lived WebSocket streams to monitored agents:\n\n- `POST /api/v1/terminal` \u2192 `createTerminal()` (terminal.go:27-67)\n- `POST /api/v1/file` \u2192 `createFM()` (fm.go:28-67)\n\nBoth call `rpc.NezhaHandlerSingleton.CreateStream(streamId, ...)` which inserts a new `ioStreamContext` into an **unbounded** `map[string]*ioStreamContext` (`s.ioStreams` in `io_stream.go:59-67`). There is **no per-user rate limit, no global semaphore, and no per-server connection cap**. Each stream allocates:\n\n1. A `ioStreamContext` struct with several channels and sync primitives\n2. Two goroutines via `StartStream()` (io_stream.go:358-369) \u2014 bidirectional `io.CopyBuffer`\n3. A gRPC IOStream between the dashboard and the agent\n4. An agent-side PTY/shell process\n\n**Vulnerable code:**\n\n`terminal.go:27-67` \u2014 `createTerminal`:\n```go\nfunc createTerminal(c *gin.Context) (*model.CreateTerminalResponse, error) {\n    // ... validation ...\n    rpc.NezhaHandlerSingleton.CreateStream(streamId, getUid(c), server.ID)\n    // ... sends TaskTypeTerminalGRPC to agent ...\n    return \u0026model.CreateTerminalResponse{...}, nil\n}\n```\n\n`fm.go:28-67` \u2014 `createFM`:\n```go\nfunc createFM(c *gin.Context) (*model.CreateFMResponse, error) {\n    // ... validation ...\n    rpc.NezhaHandlerSingleton.CreateStream(streamId, getUid(c), server.ID)\n    // ... sends TaskTypeFM to agent ...\n    return \u0026model.CreateFMResponse{...}, nil\n}\n```\n\n`io_stream.go:55-67` \u2014 `CreateStreamWithPurpose` (inserts into unbounded map):\n```go\nfunc (s *NezhaHandler) CreateStreamWithPurpose(...) {\n    s.ioStreamMutex.Lock()\n    defer s.ioStreamMutex.Unlock()\n    s.ioStreams[streamId] = \u0026ioStreamContext{\n        creatorUserID:  creatorUserID,\n        targetServerID: targetServerID,\n        purpose:        purpose,\n        userIoConnectCh:  make(chan struct{}),\n        agentIoConnectCh: make(chan struct{}),\n        revokedCh:        make(chan struct{}),\n    }\n}\n```\n\n`io_stream.go:319-372` \u2014 `StartStream` spawns two goroutines per stream:\n```go\nfunc (s *NezhaHandler) StartStream(streamId string, timeout time.Duration) error {\n    // ...\n    go func() {\n        _, innerErr := io.CopyBuffer(userIo, agentIo, bp.buf)\n        errCh \u003c- innerErr\n    }()\n    go func() {\n        _, innerErr := io.CopyBuffer(agentIo, userIo, bp.buf)\n        errCh \u003c- innerErr\n    }()\n    return \u003c-errCh\n}\n```\n\nThe `NezhaHandler.ioStreams` map is initialized as a plain `make(map[string]*ioStreamContext)` in `nezha.go:36` \u2014 no capacity limit, no eviction policy beyond explicit `CloseStream` / `RevokeStreamsForServer`.\n\nThe `HasPermission` check at terminal.go:41-43 and fm.go:43-45 controls **access scope** but does **not** limit creation volume. A user with `ScopeServerExec` (terminal) or `ScopeServerRead+Write+Delete` (file manager) can open unlimited streams.\n\n## 2. PoC\n\nA conceptual attack (no Docker needed):\n\n```\n# As an authenticated user with a valid JWT or PAT:\nfor i in {1..1000}; do\n  curl -X POST \"https://dashboard.example.com/api/v1/terminal\" \\\n    -H \"Authorization: Bearer $JWT\" \\\n    -H \"Content-Type: application/json\" \\\n    -d \u0027{\"server_id\": 1}\u0027 \u0026\ndone\nwait\n```\n\nEach request:\n- Creates a new stream entry in `ioStreams`\n- Sends a `TaskTypeTerminalGRPC` task to the agent\n- When the WebSocket attachment occurs (`GET /ws/terminal/{id}`), spawns 2 goroutines for I/O relay and allocates a 1 MB buffer per goroutine\n\nThe attack targets three resource domains:\n1. **Dashboard memory/goroutines** \u2014 each stream adds goroutines, channels, and buffers\n2. **Agent resources** \u2014 each stream spawns a PTY/shell process on the monitored server\n3. **gRPC connection pool** \u2014 concurrent IOStreams consume gRPC multiplexing capacity\n\nThe `POST /file (createFM)` endpoint provides an alternative path with the same unbounded behavior, using `ScopeServerRead+Write+Delete` instead of `ScopeServerExec`.\n\n## 3. Impact\n\n- **Denial of Service against the dashboard**: memory exhaustion, goroutine starvation, or gRPC stream table overflow from rapid stream creation\n- **Denial of Service against monitored agents**: each terminal session spawns a PTY process on the agent \u2014 an attacker can crash or degrade all agents behind the dashboard\n- **Operational cascade**: if the dashboard OOMs, all agent monitoring and alerting is lost\n- **PAT connection-registry bypass**: rapid create-connect-disconnect cycles may evade cleanup tracking\n\nThe attack requires only authenticated access with standard scopes \u2014 no special privileges. Any team member with terminal access to a server can DoS the entire infrastructure.\n\n## 4. Remediation\n\nImplement layered rate limiting and concurrency control:\n\n1. **Per-user stream cap** in `CreateStream` \u2014 reject if the user already has N active streams (e.g., 10 per user):\n   ```go\n   func (s *NezhaHandler) CreateStreamWithPurpose(...) {\n       s.ioStreamMutex.Lock()\n       defer s.ioStreamMutex.Unlock()\n       count := 0\n       for _, ctx := range s.ioStreams {\n           if ctx.creatorUserID == creatorUserID { count++ }\n       }\n       if count \u003e= maxStreamsPerUser { return error }\n       // ... existing code ...\n   }\n   ```\n\n2. **Per-server semaphore** \u2014 limit concurrent streams to any single server (e.g., 20 per server)\n\n3. **Rate limiter on `createTerminal` and `createFM`** \u2014 mirror the existing MCP rate limiter (`mcp_ratelimit.go`) for legacy WebSocket endpoints\n\n4. **Add a configurable `MaxStreamsPerUser` / `MaxStreamsPerServer` setting** so operators can tune limits without code changes",
  "id": "GHSA-jg62-j5h6-8mpq",
  "modified": "2026-06-26T23:04:18Z",
  "published": "2026-06-26T23:04:18Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/nezhahq/nezha/security/advisories/GHSA-jg62-j5h6-8mpq"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53522"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/nezhahq/nezha"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Nezha Monitoring: Unbounded WebSocket Streams \u2014 Resource Exhaustion DoS"
}

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Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

CVE-2026-53522 (GCVE-0-2026-53522)

FKIE_CVE-2026-53522

GHSA-JG62-J5H6-8MPQ

1. Description

2. PoC

3. Impact

4. Remediation

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