oras-go blob upload vulnerable to credential forwarding via unvalidated Location header

Summary

oras-go follows a registry-controlled Location header during the monolithic blob upload flow and reuses the Authorization header from the initial POST request for the subsequent PUT request. If a malicious registry returns a cross-host Location, oras-go can send the caller's credentials to an attacker-controlled endpoint.

Affected Versions

tested: v2.6.0 (commit 03243809936cce826494b5506f724c6dc11115b1, as-of 2026-01-24) range: unknown; likely affects earlier v2.x releases that include the same upload flow

Impact

Credential leak to an attacker-controlled endpoint and client-side ssrf to a cross-host target.

Affected Component

• registry/remote/repository.go:878-916 (blobStore.completePushAfterInitialPost)

Reproduction

Attachments include poc.zip with a local-only harness (no real registry required). It runs a fake registry server that returns a cross-host Location and a second server that records whether it received Authorization.

unzip -q -o poc.zip -d /tmp/poc
cd /tmp/poc/poc-F-ORAS-LOCATION-UPLOAD-001
make canonical
make control

Recommended Fix

• validate Location before uploading (scheme + hostname + effective port) against the original request, or require an explicit opt-in allowlist for cross-host upload urls
• never forward Authorization when the upload target changes host or scheme

references

• security policy: https://github.com/oras-project/oras-go/security/policy
• vulnerable code: registry/remote/repository.go (see blobStore.completePushAfterInitialPost)