GHSA-fv92-fjc5-jj9h
MEDIUMmapstructure May Leak Sensitive Information in Logs When Processing Malformed Data
Blast Radius
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Description
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:
_, _, 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:
& 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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/go-viper/mapstructure/v2 | all versions | 2.3.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/go-viper/mapstructure/v2. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/go-viper/mapstructure/v2 to 2.3.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-fv92-fjc5-jj9h is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-fv92-fjc5-jj9h is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-fv92-fjc5-jj9h. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-fv92-fjc5-jj9h in your dependencies?
O3 detects GHSA-fv92-fjc5-jj9h across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.