GHSA-fv92-fjc5-jj9h
MEDIUMGHSA-fv92-fjc5-jj9h is a medium-severity (CVSS 5.3) vulnerability in github.com/go-viper/mapstructure/v2. O3 Security confirms whether GHSA-fv92-fjc5-jj9h is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
mapstructure May Leak Sensitive Information in Logs When Processing Malformed Data
Blast Radius
github.com/go-viper/mapstructure/v2Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
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.