GHSA-FV92-FJC5-JJ9H

Vulnerability from github – Published: 2025-06-27 16:24 – Updated: 2025-06-27 16:24
VLAI?
Summary
mapstructure May Leak Sensitive Information in Logs When Processing Malformed Data
Details

Summary

Use of this library in a security-critical context may result in leaking sensitive information, if used to process sensitive fields.

Details

OpenBao (and presumably HashiCorp Vault) have surfaced error messages from mapstructure as follows:

https://github.com/openbao/openbao/blob/98c3a59c040efca724353ca46ca79bd5cdbab920/sdk/framework/field_data.go#L43-L50

            _, _, err := d.getPrimitive(field, schema)
            if err != nil {
                return fmt.Errorf("error converting input for field %q: %w", field, err)
            }

where this calls mapstructure.WeakDecode(...): https://github.com/openbao/openbao/blob/98c3a59c040efca724353ca46ca79bd5cdbab920/sdk/framework/field_data.go#L181-L193


func (d *FieldData) getPrimitive(k string, schema *FieldSchema) (interface{}, bool, error) {
    raw, ok := d.Raw[k]
    if !ok {
        return nil, false, nil
    }

    switch t := schema.Type; t {
    case TypeBool:
        var result bool
        if err := mapstructure.WeakDecode(raw, &result); err != nil {
            return nil, false, err
        }
        return result, true, nil

Notably, WeakDecode(...) eventually calls one of the decode helpers, which surfaces the original value:

https://github.com/go-viper/mapstructure/blob/1a66224d5e54d8757f63bd66339cf764c3292c21/mapstructure.go#L679-L686

https://github.com/go-viper/mapstructure/blob/1a66224d5e54d8757f63bd66339cf764c3292c21/mapstructure.go#L726-L730

https://github.com/go-viper/mapstructure/blob/1a66224d5e54d8757f63bd66339cf764c3292c21/mapstructure.go#L783-L787

& more.

PoC

To reproduce with OpenBao:

$ podman run -p 8300:8300 openbao/openbao:latest server -dev -dev-root-token-id=root -dev-listen-address=0.0.0.0:8300

and in a new tab:

$ BAO_TOKEN=root BAO_ADDR=http://localhost:8300 bao auth enable userpass
Success! Enabled userpass auth method at: userpass/
$ curl -X PUT -H "X-Vault-Request: true" -H "X-Vault-Token: root" -d '{"password":{"asdf":"my-sensitive-value"}}' "http://localhost:8300/v1/auth/userpass/users/adsf"
{"errors":["error converting input for field \"password\": '' expected type 'string', got unconvertible type 'map[string]interface {}', value: 'map[asdf:my-sensitive-value]'"]}

Impact

This is an information disclosure bug with little mitigation. See https://discuss.hashicorp.com/t/hcsec-2025-09-vault-may-expose-sensitive-information-in-error-logs-when-processing-malformed-data-with-the-kv-v2-plugin/74717 for a previous version. That version was fixed, but this is in the second part of that error message (starting at '' expected a map, got 'string' -- when the field type is string and a map is provided, we see the above information leak -- the previous example had a map type field with a string value provided).

This was rated 4.5 Medium by HashiCorp in the past iteration.

Severity ?
5.3 (Medium)
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/go-viper/mapstructure/v2"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.3.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-532"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2025-06-27T16:24:59Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nUse of this library in a security-critical context may result in leaking sensitive information, if used to process sensitive fields.\n\n### Details\n\nOpenBao (and presumably HashiCorp Vault) have surfaced error messages from `mapstructure` as follows:\n\nhttps://github.com/openbao/openbao/blob/98c3a59c040efca724353ca46ca79bd5cdbab920/sdk/framework/field_data.go#L43-L50\n\n```go\n\t\t\t_, _, err := d.getPrimitive(field, schema)\n\t\t\tif err != nil {\n\t\t\t\treturn fmt.Errorf(\"error converting input for field %q: %w\", field, err)\n\t\t\t}\n```\n\nwhere this calls `mapstructure.WeakDecode(...)`: https://github.com/openbao/openbao/blob/98c3a59c040efca724353ca46ca79bd5cdbab920/sdk/framework/field_data.go#L181-L193\n\n```go\n\nfunc (d *FieldData) getPrimitive(k string, schema *FieldSchema) (interface{}, bool, error) {\n\traw, ok := d.Raw[k]\n\tif !ok {\n\t\treturn nil, false, nil\n\t}\n\n\tswitch t := schema.Type; t {\n\tcase TypeBool:\n\t\tvar result bool\n\t\tif err := mapstructure.WeakDecode(raw, \u0026result); err != nil {\n\t\t\treturn nil, false, err\n\t\t}\n\t\treturn result, true, nil\n```\n\nNotably, `WeakDecode(...)` eventually calls one of the decode helpers, which surfaces the original value:\n\nhttps://github.com/go-viper/mapstructure/blob/1a66224d5e54d8757f63bd66339cf764c3292c21/mapstructure.go#L679-L686\n\nhttps://github.com/go-viper/mapstructure/blob/1a66224d5e54d8757f63bd66339cf764c3292c21/mapstructure.go#L726-L730\n\nhttps://github.com/go-viper/mapstructure/blob/1a66224d5e54d8757f63bd66339cf764c3292c21/mapstructure.go#L783-L787\n\n\u0026 more.\n\n### PoC\n\nTo reproduce with OpenBao:\n\n```\n$ podman run -p 8300:8300 openbao/openbao:latest server -dev -dev-root-token-id=root -dev-listen-address=0.0.0.0:8300\n```\n\nand in a new tab:\n\n```\n$ BAO_TOKEN=root BAO_ADDR=http://localhost:8300 bao auth enable userpass\nSuccess! Enabled userpass auth method at: userpass/\n$ curl -X PUT -H \"X-Vault-Request: true\" -H \"X-Vault-Token: root\" -d \u0027{\"password\":{\"asdf\":\"my-sensitive-value\"}}\u0027 \"http://localhost:8300/v1/auth/userpass/users/adsf\"\n{\"errors\":[\"error converting input for field \\\"password\\\": \u0027\u0027 expected type \u0027string\u0027, got unconvertible type \u0027map[string]interface {}\u0027, value: \u0027map[asdf:my-sensitive-value]\u0027\"]}\n```\n\n### Impact\n\nThis is an information disclosure bug with little mitigation. See https://discuss.hashicorp.com/t/hcsec-2025-09-vault-may-expose-sensitive-information-in-error-logs-when-processing-malformed-data-with-the-kv-v2-plugin/74717 for a previous version. That version was fixed, but this is in the second part of that error message (starting at `\u0027\u0027 expected a map, got \u0027string\u0027` -- when the field type is `string` and a `map` is provided, we see the above information leak -- the previous example had a `map` type field with a `string` value provided).\n\nThis was rated 4.5 Medium by HashiCorp in the past iteration.",
  "id": "GHSA-fv92-fjc5-jj9h",
  "modified": "2025-06-27T16:24:59Z",
  "published": "2025-06-27T16:24:59Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/go-viper/mapstructure/security/advisories/GHSA-fv92-fjc5-jj9h"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/go-viper/mapstructure"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "mapstructure May Leak Sensitive Information in Logs When Processing Malformed Data"
}


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