Why do unknown certificates create both security and availability risk?

Why This Matters for Security Teams

Unknown certificates are not just a housekeeping problem. They are machine credentials, so every unmanaged certificate expands the identity estate without a clear owner, policy, or renewal path. That creates two failure modes at once: outage risk when a certificate expires, and trust risk when an untracked credential continues to authenticate systems that no one can confidently govern. NIST’s NIST Cybersecurity Framework 2.0 treats this as a governance and resilience issue, not a narrow PKI task.

The operational lesson is straightforward. Certificates that are “somewhere in the environment” but not in a named inventory cannot be monitored, rotated, or revoked with confidence. NHIMG research on machine identity management gaps found that 45% of organisations say certificate expiry is the leading cause of outages, which shows how quickly hidden technical debt becomes visible downtime. In practice, many security teams encounter the problem only after an expiry event or trust failure has already disrupted production, rather than through intentional inventory control.

How It Works in Practice

Unknown certificates usually appear in edge cases that traditional asset management misses: old load balancers, application servers, service meshes, CI/CD pipelines, embedded devices, or shadow IT deployments. The risk is not limited to public TLS. Internal certificates, client authentication certificates, mutual TLS credentials, signing certificates, and API gateway trust chains all need ownership and lifecycle controls. Without those controls, a certificate can quietly drift out of compliance, remain in use after a team has changed, or survive long after the system it protects should have been retired.

Effective management starts with discovery, then moves to assignment, policy, and renewal automation. That means building a complete inventory, mapping each certificate to a service owner, defining expiration thresholds, and integrating renewal into operational workflows. NIST guidance on continuous monitoring and the NIST Key Management guidance supports this lifecycle view, while NHIMG’s Top 10 NHI Issues research frames certificates as part of broader non-human identity governance.

• Discover certificates across clouds, endpoints, applications, and network appliances.
• Assign each certificate to an owner, service, and renewal process.
• Track expiry, issuance, revocation, and key material rotation as controlled events.
• Alert on certificates that lack ownership, policy, or telemetry.
• Prioritise externally exposed and authentication-bearing certificates first.

This becomes especially important when certificates are embedded in automation, because machines do not request exceptions or extension windows. These controls tend to break down when certificates are generated ad hoc in development pipelines or stored in unmanaged secrets stores because ownership and expiry telemetry are absent.

Common Variations and Edge Cases

Tighter certificate governance often increases operational overhead, requiring organisations to balance resilience against the friction of inventory upkeep and renewal automation. That tradeoff is real, and current guidance suggests the best approach is evolving from periodic audits toward continuous control. There is no universal standard for every certificate class, especially where legacy systems, third-party appliances, or regulated environments constrain automation.

Some certificates are low risk on their own but still matter because they sit inside a trust chain. Others, such as code-signing or mTLS certificates, can be higher impact even when they are not internet-facing. Teams should also separate “unknown” from “unowned”: an unowned certificate may have a technical location, but if no business or service owner can be named, it is still a governance failure. In identity terms, this is where NHI discipline matters, because a certificate is not just configuration data, it is a credential that confers machine trust. For deeper context on that identity boundary, see Ultimate Guide to NHIs — What are Non-Human Identities and the machine identity management gaps findings.

In regulated environments, the question is not whether a certificate is expired, but whether the organisation can prove control over discovery, ownership, and renewal before an audit or incident exposes the gap.

Related resources from NHI Mgmt Group

• Why do unknown assets create both security and compliance risk?
• Why do DNS misconfigurations create both availability and security risk?
• Why do broad DNS permissions create both security and availability risk?
• What is secrets sprawl and why does it create security risk?