Build phase storage hard codes the secret into the image or manifest, which makes it persistent, inspectable, and easy to redistribute through registries. Runtime supply keeps the image generic and injects the secret only when the container starts. That distinction matters because runtime injection reduces exposure, limits persistence, and aligns secret handling with the actual execution context.
Why build-time secrets become persistent exposure
Build-time storage changes a secret from an operational input into part of the artifact. Once it is embedded in an image layer, manifest, or build log, the secret can be copied, cached, scanned, and redistributed far beyond the original pipeline. That is why hardened build systems treat secret handling as a supply-chain control, not just a convenience choice.
When build-time handling is unavoidable, the real question is not whether the secret is “in the container,” but how many places now hold a recoverable copy. NIST SP 800-190 Container Security is useful here because it frames images, registries, and runtime separation as distinct control points. Guide to the Secret Sprawl Challenge shows why hardcoded credentials, CI/CD exposure, and remediation problems tend to amplify each other once secrets enter build outputs.
Build-time storage also makes rollback and reuse dangerous. A rebuilt or republished image may still carry the old value, and that value may remain recoverable even after the application is redeployed. For teams that use artifact promotion across environments, the secret becomes part of the artifact’s blast radius rather than a property of one execution context.
How runtime injection keeps the image generic
Runtime supply keeps the container image reusable because the secret is introduced only when the workload starts. That preserves a clean separation between code and secret material, which reduces accidental disclosure through source control, registries, and shared artifacts. It also makes replacement simpler because you can rotate the secret without rebuilding the image.
The practical advantage is context binding. A runtime-injected secret can be limited to the environment, identity, or session that actually needs it, rather than being frozen into a file that travels everywhere the image travels. RFC 7523: JWT Profile for OAuth 2.0 Client Authentication and Authorization Grants is a good example of the broader pattern, using short-lived assertions instead of embedded shared secrets. Secrets Management Guide reinforces the same operational idea: keep secrets out of the static artifact and move toward injection, rotation, and secretless patterns where possible.
Runtime injection is not magic, though. The secret still exists somewhere at execution time, so the implementation must control who can read it, how long it lives in memory, and whether it is written to logs, environment dumps, or crash reports. That makes the runtime path safer than build-time embedding, but only if the surrounding platform enforces tight access and short exposure windows.
What changes operationally when you move the secret to runtime
The biggest change is lifecycle control. Build-time storage ties secret validity to the artifact lifecycle, while runtime injection ties it to the execution lifecycle. That means rotation, revocation, and environment separation become much easier to manage, because you are updating a secret source rather than rebuilding every dependent image.
It also changes where failure shows up. With build-time storage, a leak may persist unnoticed in a registry, cache, or copied image for a long time. With runtime supply, the common failure modes are mis-scoped access, overly broad retrieval permissions, or secrets that are injected correctly but exposed later through misconfiguration. OWASP Non-Human Identity Top 10 is relevant because the same secret-handling mistakes often drive overprivilege, long-lived secrets, and secret leakage in automated systems.
Risk and Threat Considerations
Build-time secret storage increases the chance that a single secret becomes many recoverable copies. Once that happens, an attacker only needs one exposed layer, registry snapshot, CI log, or copied image to gain reusable access, and revocation becomes harder because the value may already be circulating.
Failure mechanism: the secret is baked into an artifact that is designed to be copied, cached, and promoted, so disclosure can occur long after the original build is forgotten. Attackers and internal users alike can abuse that persistence if the artifact or its history is exposed.
Impact: credential rotation becomes slower and less reliable, the blast radius expands across environments, and compromise can continue even after the application is redeployed. Runtime injection reduces that persistence, but only if the secret source is protected and the runtime path does not leak the value into logs or debug output.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP Non-Human Identity Top 10 addresses the attack and risk surface, while NIST SP 800-53 Rev 5 and OWASP ASVS set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST SP 800-53 Rev 5 | IA-5 — Authenticator Management | Covers secret lifecycle control and rotation for credentials used by workloads. |
| IA-9 — Service Identification and Authentication | Applies when services authenticate to each other using runtime-delivered credentials. | |
| CM-6 — Configuration Settings | Build-time secret embedding is a configuration control failure affecting deployment integrity. | |
| Recommendation — Rotate and revoke secrets through a managed lifecycle instead of embedding them in build artifacts. Use runtime-delivered service credentials rather than baking shared secrets into images. Keep deployment artifacts secret-free and inject environment-specific values at runtime. | ||
| OWASP ASVS | V14 — Data Protection | Addresses protection of sensitive values in application and deployment handling. |
| Recommendation — Store secrets outside source and artifacts, and protect them throughout the application lifecycle. | ||
| OWASP Non-Human Identity Top 10 | NHI-02 — Secret Leakage | Directly covers the risk of secrets being exposed through artifacts, logs, or repositories. |
| Recommendation — Prevent secret leakage by injecting secrets at runtime and keeping artifacts free of sensitive values. | ||
Practitioner Guidance
What to verify: confirm that no production secret is present in the image filesystem, build cache, Dockerfile history, or deployment manifest. If the secret can be extracted from the artifact without accessing the running workload, treat that as a design failure, not just a hygiene issue.
Decision rule: if a secret is required only when the workload starts, inject it at runtime and keep the image secret-free. If the artifact must retain a value for functionality, challenge whether that value should be a secret at all, or whether it should be replaced with a short-lived credential or token flow.
Practitioner takeaway: build-time storage turns a secret into distributed artifact risk, while runtime supply keeps the secret aligned to execution and makes rotation and containment far more manageable.
Related resources from NHI Mgmt Group
- What is the difference between storing secrets in docker-compose files and injecting them at runtime from a secrets manager?
- What is the difference between storing CI/CD secrets in pipeline variables and retrieving them from a central secrets manager at runtime?
- What is the difference between storing secrets in a vault and exposing them at runtime through an environment layer?
- What is the difference between storing secrets in code and loading them from a service account at runtime?
Deepen Your Knowledge
Reviewed and updated by the NHIMG editorial team on September 29, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org
