Vulnerability-Lookup

GHSA-JCC7-9WPM-MJ36

Vulnerability from github – Published: 2026-03-17 15:29 – Updated: 2026-03-25 18:51

Summary

Next.js: null origin can bypass dev HMR websocket CSRF checks

Details

Summary

In next dev, cross-site protections for internal development endpoints could treat Origin: null as a bypass case even when allowedDevOrigins is configured. This could allow privacy-sensitive or opaque browser contexts, such as sandboxed documents, to access privileged internal dev-server functionality unexpectedly.

Impact

If a developer visits attacker-controlled content while running an affected next dev server with allowedDevOrigins configured, attacker-controlled browser code may be able to connect to internal development endpoints and interact with sensitive dev-server functionality that should have remained blocked.

This issue affects development mode only. It does not affect next start, and it does not expose internal debugging functionality to the network by default.

Patches

Fixed by validating Origin: null through the same cross-site origin-allowance checks used for other origins on internal development endpoints.

Workarounds

If upgrade is not immediately possible: - Do not expose next dev to untrusted networks. - If you use allowedDevOrigins, reject requests and websocket upgrades with Origin: null for internal dev endpoints at your proxy.

Severity ?

2.3 (Low)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "next"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "16.0.1"
            },
            {
              "fixed": "16.1.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-27977"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1385"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-17T15:29:48Z",
    "nvd_published_at": "2026-03-18T00:16:19Z",
    "severity": "LOW"
  },
  "details": "## Summary\nIn `next dev`, cross-site protections for internal development endpoints could treat `Origin: null` as a bypass case even when [`allowedDevOrigins`](https://nextjs.org/docs/app/api-reference/config/next-config-js/allowedDevOrigins) is configured. This could allow privacy-sensitive or opaque browser contexts, such as sandboxed documents, to access privileged internal dev-server functionality unexpectedly.\n\n## Impact\nIf a developer visits attacker-controlled content while running an affected `next dev` server with [`allowedDevOrigins`](https://nextjs.org/docs/app/api-reference/config/next-config-js/allowedDevOrigins) configured, attacker-controlled browser code may be able to connect to internal development endpoints and interact with sensitive dev-server functionality that should have remained blocked.\n\nThis issue affects development mode only. It does not affect `next start`, and it does not expose internal debugging functionality to the network by default.\n\n## Patches\nFixed by validating `Origin: null` through the same cross-site origin-allowance checks used for other origins on internal development endpoints.\n\n## Workarounds\nIf upgrade is not immediately possible:\n- Do not expose `next dev` to untrusted networks.\n- If you use [`allowedDevOrigins`](https://nextjs.org/docs/app/api-reference/config/next-config-js/allowedDevOrigins), reject requests and websocket upgrades with `Origin: null` for internal dev endpoints at your proxy.",
  "id": "GHSA-jcc7-9wpm-mj36",
  "modified": "2026-03-25T18:51:19Z",
  "published": "2026-03-17T15:29:48Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/vercel/next.js/security/advisories/GHSA-jcc7-9wpm-mj36"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-27977"
    },
    {
      "type": "WEB",
      "url": "https://github.com/vercel/next.js/commit/862f9b9bb41d235e0d8cf44aa811e7fd118cee2a"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/vercel/next.js"
    },
    {
      "type": "WEB",
      "url": "https://github.com/vercel/next.js/releases/tag/v16.1.7"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Next.js: null origin can bypass dev HMR websocket CSRF checks"
}

CVE-2026-27977 (GCVE-0-2026-27977)

Vulnerability from cvelistv5 – Published: 2026-03-17 23:56 – Updated: 2026-03-18 19:56

Title

Next.js: null origin can bypass dev HMR websocket CSRF checks

Summary

Next.js is a React framework for building full-stack web applications. Starting in version 16.0.1 and prior to version 16.1.7, in `next dev`, cross-site protection for internal websocket endpoints could treat `Origin: null` as a bypass case even if `allowedDevOrigins` is configured, allowing privacy-sensitive/opaque contexts (for example sandboxed documents) to connect unexpectedly. If a dev server is reachable from attacker-controlled content, an attacker may be able to connect to the HMR websocket channel and interact with dev websocket traffic. This affects development mode only. Apps without a configured `allowedDevOrigins` still allow connections from any origin. The issue is fixed in version 16.1.7 by validating `Origin: null` through the same cross-site origin-allowance checks used for other origins. If upgrading is not immediately possible, do not expose `next dev` to untrusted networks and/or block websocket upgrades to `/_next/webpack-hmr` when `Origin` is `null` at the proxy.

Severity ?

2.3 (Low)


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

CWE

CWE-1385 - Missing Origin Validation in WebSockets

Assigner

GitHub_M

References

URL

Tags

	https://github.com/vercel/next.js/security/adviso…	x_refsource_CONFIRM
	https://github.com/vercel/next.js/commit/862f9b9b…	x_refsource_MISC
	https://github.com/vercel/next.js/releases/tag/v16.1.7	x_refsource_MISC

Impacted products

	Vendor	Product	Version
	vercel	next.js	Affected: >= 16.0.1, < 16.1.7

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-27977",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-03-18T19:56:08.547586Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-03-18T19:56:16.843Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "next.js",
          "vendor": "vercel",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 16.0.1, \u003c 16.1.7"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Next.js is a React framework for building full-stack web applications. Starting in version 16.0.1 and prior to version 16.1.7, in `next dev`, cross-site protection for internal websocket endpoints could treat `Origin: null` as a bypass case even if `allowedDevOrigins` is configured, allowing privacy-sensitive/opaque contexts (for example sandboxed documents) to connect unexpectedly. If a dev server is reachable from attacker-controlled content, an attacker may be able to connect to the HMR websocket channel and interact with dev websocket traffic. This affects development mode only. Apps without a configured `allowedDevOrigins` still allow connections from any origin. The issue is fixed in version 16.1.7 by validating `Origin: null` through the same cross-site origin-allowance checks used for other origins. If upgrading is not immediately possible, do not expose `next dev` to untrusted networks and/or block websocket upgrades to `/_next/webpack-hmr` when `Origin` is `null` at the proxy."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "PRESENT",
            "attackVector": "NETWORK",
            "baseScore": 2.3,
            "baseSeverity": "LOW",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "PASSIVE",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "LOW",
            "vulnIntegrityImpact": "LOW"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-1385",
              "description": "CWE-1385: Missing Origin Validation in WebSockets",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-03-18T00:23:47.523Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/vercel/next.js/security/advisories/GHSA-jcc7-9wpm-mj36",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/vercel/next.js/security/advisories/GHSA-jcc7-9wpm-mj36"
        },
        {
          "name": "https://github.com/vercel/next.js/commit/862f9b9bb41d235e0d8cf44aa811e7fd118cee2a",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/vercel/next.js/commit/862f9b9bb41d235e0d8cf44aa811e7fd118cee2a"
        },
        {
          "name": "https://github.com/vercel/next.js/releases/tag/v16.1.7",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/vercel/next.js/releases/tag/v16.1.7"
        }
      ],
      "source": {
        "advisory": "GHSA-jcc7-9wpm-mj36",
        "discovery": "UNKNOWN"
      },
      "title": "Next.js: null origin can bypass dev HMR websocket CSRF checks"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-27977",
    "datePublished": "2026-03-17T23:56:24.631Z",
    "dateReserved": "2026-02-25T03:24:57.793Z",
    "dateUpdated": "2026-03-18T19:56:16.843Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date

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.

Action not permitted

GHSA-JCC7-9WPM-MJ36

Summary

Impact

Patches

Workarounds

CVE-2026-27977 (GCVE-0-2026-27977)

Tags

Sightings

Nomenclature