Hop-by-hop abuse to malform header mutator
What to do
Vendor fix available. Upgrade each affected package to the fixed version on its release line (github.com/ory/oathkeeper 0.40.3), redeploy, then verify what is actually installed.
This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.
Affected packages
- Affected
- < 0.40.3
- Fixed in
- 0.40.3
Sources
- GitHub Advisory Database and maintainer security advisories on GitHub
GitHub-reviewed advisory GHSA-w9mr-28mw-j8hg lists affected ranges: Go github.com/ory/oathkeeper >=0 <0.40.3
VerifiedObserved Structured GitHub Advisory Database record (type=reviewed) from the GitHub REST API.
Severity and exploitation
- Exploitation
- No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
- CVSS
- not scored
- EPSS
- No dated EPSS signal available.
Source description
As published by the source; long descriptions are shortened.
Impact Downstream services relying on the presence of headers set by the header mutator could be exploited. A client can drop the header set by the header mutator by including that header's name in the Connection header. Example minimal config: The X-Subject header will not arrive at the downstream server. It is completely dropped. In case the downstream server handles such a request in an unexpected way, an attacker can exploit this, assuming they know or guess the internal header name. Patches c5cc7f736dc84185034be4356057d1c7a656d797 Workarounds The downstream server should handle the case that an expected header is not set by responding with an appropriate error. References See background info in https://github.com/golang/go/issues/50580
Dates and revisions
- Published by the source
- Last modified by the source
- Source last checked
- Revision 1 · created ·
Published from ghsa record GHSA-w9mr-28mw-j8hg
Agent brief
Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.
# Patch Next advisory brief: GHSA-w9mr-28mw-j8hg Advisory: Hop-by-hop abuse to malform header mutator IDs: GHSA-w9mr-28mw-j8hg Record: https://patchnext.com/advisories/ghsa-w9mr-28mw-j8hg (revision 1, source checked 26 Oct 2026, 14:58 UTC) Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected. Severity: Unrated Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV. Vendor response: Vendor fix available; fixed versions by package: github.com/ory/oathkeeper 0.40.3. A vendor fix does not mean a deployment is fixed. ## Affected components - Go github.com/ory/oathkeeper: affected < 0.40.3; fixed in 0.40.3 ## Suggested inspection (read-only) - Go github.com/ory/oathkeeper: 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/ory/oathkeeper. - 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-w9mr-28mw-j8hg (GitHub-reviewed advisory GHSA-w9mr-28mw-j8hg lists affected ranges: Go github.com/ory/oathkeeper >=0 <0.40.3) Commands are suggestions: review each one before running it.
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