CVE-2026-108126temporal-proxy payload decryption is not bound to the request namespace

Official description

temporal-proxy 0.2.0 through 0.8.0 does not bind encrypted payloads to the namespace they were encrypted for. When payload encryption is enabled, the proxy chooses the decryption key by an identifier stored in the payload rather than by the namespace of the request, and nothing in the ciphertext records that namespace. A caller whom the proxy authorizes only for namespace B, and who has obtained an encrypted payload from namespace A, can therefore have the proxy decrypt it. In 0.8.0, the caller can submit the payload to the codec server's /decode endpoint. In every affected version, a caller who can also write to namespace B on the Temporal server directly can place the payload there and read it back through the proxy. This holds whether namespaces share the default key or each has its own, because a single proxy holds every key it is configured with. The issue does not give the attacker encrypted payloads they could not already obtain, and does not allow encrypted payloads to be modified.

Affected products (as reported)

References

• Vault.Open in temporal-proxy 0.8.0, which takes no namespace product
• KEKRegistry.Decrypt in temporal-proxy 0.8.0, which selects the KEK by the identifier in the payload product
• AES-256-GCM sealed and opened with no associated data in temporal-proxy 0.8.0 product
• Design discussion of associated data in the payload encryption scheme technical-description
• Fix pull request patch
• Fix commit patch
• Codec server fix pull request patch
• Codec server fix commit patch
• temporal-proxy 0.9.0 release-notes