PKCE proves the same client started the login flow without storing a reusable secret inside the application. Embedding a client secret in a public binary exposes a credential that can be extracted and abused. For CLI tools, PKCE is the safer model because it supports public clients, preserves interactive sign in, and removes the need to ship secrets with the executable.
Why PKCE Fits Public CLI Tools Better Than Shared Secrets
The difference is not just convenience. A public CLI binary is easy to copy, inspect, and run in untrusted environments, so any embedded client secret becomes a reusable credential rather than an application setting. PKCE avoids that problem by binding the login exchange to the original client session without requiring a secret that every user or attacker can extract from the executable. That makes it the right pattern for tools that must sign users in interactively but cannot safely hold a long-lived credential.
For teams building CLI authentication, the key design choice is whether the software is truly a confidential client. If the answer is no, then a client secret in the binary creates unnecessary exposure and weakens the trust boundary between the build artifact and the identity system. NHI Management Group has documented how static credentials in code and tooling are a recurring source of exposure, and its Ultimate Guide to NHIs — Static vs Dynamic Secrets explains why short-lived, purpose-bound credentials are usually the safer model.
In practice, many teams discover the danger only after the binary has already been distributed broadly and the secret is treated as effectively public.
How PKCE Works in a CLI Authentication Flow
PKCE changes the login flow so the CLI proves continuity across the exchange instead of proving possession of a stored secret. The tool generates a one-time code verifier, derives a code challenge, starts the sign-in flow, and later redeems the authorization code using the verifier. Because the verifier is generated per session and not shipped with the app, there is nothing durable for an attacker to extract from the binary and reuse at scale.
This is why PKCE is a strong fit for public client, including desktop apps and command-line tools. The application can still complete an interactive sign-in, receive tokens, and operate on behalf of the user, but it does so without embedding an authentication secret that must remain confidential. The practical security gain is blast-radius reduction: compromise of the binary does not automatically compromise the client credential itself.
By contrast, embedding a client secret in a public binary turns the build artifact into a credential container. Anyone with access to the file can reverse engineer it, decompile it, or inspect strings and configuration to recover the secret. Once exposed, that secret may be used to impersonate the application, abuse token flows, or create persistent access that is hard to distinguish from legitimate use. The OWASP Non-Human Identity Top 10 is relevant here because it treats machine-held credentials as a governance and abuse surface, not just a convenience feature for developers.
- Use PKCE when the client cannot keep a secret confidential across all users and hosts.
- Use short-lived authorization artifacts rather than a reusable embedded credential.
- Keep the binary public-facing, but keep the trust decision anchored in the interactive flow and token policy.
These controls tend to break down when a CLI is repackaged as a service account client or shared across automation contexts, because the application stops behaving like a public client and starts needing stronger workload identity controls.
Where the Tradeoff Shows Up in Real Deployments
Tighter authentication design often increases integration effort, so teams sometimes reach for a client secret because it seems simpler to ship and support. That shortcut creates a real tradeoff: ease of implementation versus exposure of a credential that cannot practically stay secret in a public distribution model. PKCE is not a universal replacement for all client authentication; it is the better fit when the tool is public and the threat model includes reverse engineering, repackaging, or credential extraction.
There is also an operational distinction between user sign-in and machine-to-machine access. If the CLI is acting on behalf of a human, PKCE preserves interactive sign-in without storing a reusable secret. If the software is actually an unattended automation workload, then best practice is evolving toward workload identity, scoped secrets, or a different non-interactive trust model rather than trying to make PKCE do a job it was not designed to do. That distinction matters because the wrong pattern can create brittle authentication and hidden access paths.
For governance and assurance, the practical question is whether the credential can survive exposure without becoming an account takeover primitive. If the answer is no, the secret does not belong in the binary. For broader identity risk context, NHI Management Group’s Guide to the Secret Sprawl Challenge is useful because it shows how quickly embedded secrets become difficult to inventory, rotate, and revoke once they leave controlled storage. Current guidance suggests treating any public binary with a long-lived client secret as a preventable exposure, not an acceptable implementation shortcut.
In practice, the failure usually appears when a seemingly harmless CLI is reused in scripts, CI jobs, or shared endpoints, and the original public-client assumption no longer matches reality.
Risk and Threat Considerations
Embedding a client secret in a public binary creates a credential exposure problem, not just a code hygiene problem. The risk is that the secret is no longer secret once the executable is distributed, copied, or inspected, and the resulting credential can be replayed by anyone who extracts it. PKCE reduces that exposure by removing the durable secret from the client side and binding the exchange to the live login session.
Failure mechanism: Attackers or opportunistic users recover the embedded secret through binary inspection, strings extraction, decompilation, or configuration leakage, then use it to impersonate the client or automate unauthorized token requests. Because the credential is reusable, compromise persists until the secret is rotated and every dependent integration is updated.
Impact: The application identity can be abused at scale, token issuance can be unauthorised, and revocation becomes slow and disruptive because the same secret may be embedded in multiple builds, forks, or downstream packages.
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 and MITRE ATT&CK address the attack and risk surface, while NIST CSF 2.0 and CIS Controls v8 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Non-Human Identity Top 10 | NHI-01 — Secrets and Credential Management | Public binaries should not carry reusable client secrets. |
| NHI-02 — Identity Lifecycle and Rotation | Extracted client secrets must be rotatable and revocable at scale. | |
| Recommendation — Remove embedded secrets and use ephemeral, session-bound authentication instead. Design credentials so you can revoke and rotate them without redeploying every client. | ||
| NIST CSF 2.0 | PR.AC-1 — Identity and Access Management | The issue is choosing the right authentication control for the client type. |
| Recommendation — Apply the correct access model for public clients rather than assuming a secret can stay confidential. | ||
| CIS Controls v8 | 6.3 — Data Protection | Embedded secrets in binaries are exposed data that needs protection and removal. |
| Recommendation — Eliminate secrets from distributed code and store them in controlled secret systems. | ||
| MITRE ATT&CK | T1552 — Unsecured Credentials | Embedded secrets in public binaries are a credential exposure pattern. |
| Recommendation — Hunt for exposed credentials in binaries and rotate anything that can be extracted. | ||
Practitioner Guidance
What to prioritise: Decide first whether the CLI is a public client or an unattended automation client. If users install and run the binary themselves, treat embedded secrets as an avoidable exposure and prefer PKCE with short-lived tokens.
Decision rule: If the secret would be unsafe to publish in source code, it is also unsafe to ship inside a public executable. If the tool truly needs non-interactive access, redesign it as a workload identity problem rather than disguising it as a CLI login problem.
What to verify: Confirm that no build output, crash log, support bundle, or updater package contains reusable client material. Also verify that rotation and revocation are workable without forcing a full client redeployment.
Practitioner takeaway: The right authentication model is the one that survives distribution; for public CLIs, that usually means proving the session with PKCE instead of trying to hide a secret that attackers can eventually extract.
Related resources from NHI Mgmt Group
- What is the difference between client secret authentication and certificate-based authentication for service principals?
- What is the difference between static secrets and certificate-based authentication for API security?
- What is the difference between certificate-based authentication and federated identity provider based access?
- What is the difference between SSH public key authentication and SSH certificate-based authentication?
Deepen Your Knowledge
Reviewed and updated by the NHIMG editorial team on September 10, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org
