mapstructure May Leak Sensitive Information in Logs When Processing Malformed Data

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.3 · CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

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/fielddata.go#L43-L50 where this calls mapstructure.WeakDecode(...): https://github.com/openbao/openbao/blob/98c3a59c040efca724353ca46ca79bd5cdbab920/sdk/framework/fielddata.go#L181-L193 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…

Published by the source

27 Jun 2025, 16:24 UTC

Last modified by the source

27 Jun 2025, 16:24 UTC

Source last checked

26 Oct 2026, 15:09 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-fv92-fjc5-jj9h

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# Patch Next advisory brief: GHSA-fv92-fjc5-jj9h

Advisory: mapstructure May Leak Sensitive Information in Logs When Processing Malformed Data
IDs: GHSA-fv92-fjc5-jj9h
Record: https://patchnext.com/advisories/ghsa-fv92-fjc5-jj9h (revision 1, source checked 26 Oct 2026, 15:09 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/go-viper/mapstructure/v2 2.3.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/go-viper/mapstructure/v2: affected < 2.3.0; fixed in 2.3.0

## Suggested inspection (read-only)
- Go github.com/go-viper/mapstructure/v2: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/go-viper/mapstructure/v2.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-fv92-fjc5-jj9h (GitHub-reviewed advisory GHSA-fv92-fjc5-jj9h lists affected ranges: Go github.com/go-viper/mapstructure/v2 >=0 <2.3.0)

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