SSL/TSL certificates are one of the most fundamental tools organizations rely on. But not all certificates offer the same level of trust. Self-signed certificates, while easy and cost-free to generate, create hidden vulnerabilities that can quietly erode your security posture. Without the validation provided by a trusted certificate authority (CA), self-signed certificates make it difficult for your team to confirm authenticity, open the door to man-in-the-middle attacks, and complicate compliance efforts.
While self-signed certificates do have legitimate uses, using a self-signed certificate in the wrong context can open your organization up to risk. For this reason, it’s critical to know when to appropriately use a self-signed certificate, and when it may be a security liability.
What is a self-signed certificate?
A self-signed certificate is any type of digital certificate that is signed by the same entity that issued it. Unlike other CA signed certificates, which are signed by a publicly trusted certificate authority, self-signed certificates have no external, independent authority vouching for their legitimacy.
This causes problems when a browser or application encounters a self-signed certificate and has no independent way to verify the server’s identity. A site sees an identity claim without any credible endorsement, and may respond by generating security warnings.
What are the differences between self-signed and CA-signed certificates?
Although self-signed and CA-signed certificates may look similar on the surface, their trust models, validation processes, and security implications are entirely different.
- Self-signed certificates are created and signed by the same entity. The organization (or individual) issuing the certificate is also the one vouching for its legitimacy. Because no trusted third party is involved, clients have no basis for trusting the certificate unless they manually configure that trust.
- CA-signed certificates, on the other hand, are issued by publicly trusted Certificate Authorities. These CAs undergo strict audits, follow industry-standard policies, and are included in the trusted root stores of browsers, operating systems, network appliances, and applications.
The key difference between the two certificate types lies in the chain of trust, the foundation of the public key infrastructure (PKI).
A CA-signed certificate is part of a hierarchical trust chain:
- Root CA : A highly secure, widely trusted authority baked into client trust stores.
- Intermediate CA: Subordinate authorities that issue certificates on behalf of the root.
- End-entity certificate: The certificate installed on a server, application, or device.
When a client connects to a server, it validates each link in this chain. If the chain successfully traces back to a trusted root CA, the connection is considered authentic and secure.
A self-signed certificate, however, has no chain. Anyone can generate one for any domain or identity they choose, which is precisely why they are not trusted. This lack of chain of trust is the core reason self-signed certificates trigger warnings, break automations, and undermine security posture.
What are some use cases for self-signed certificates?
Despite their lack of public trust, self-signed certificates are not without purpose. In controlled, non-public environments where trust can be established manually and risks are understood, they can be a practical tool. Their use cases are strictly limited to scenarios where external validation is unnecessary or impossible, however.
Local development and testing environments
One of the most common and acceptable uses for self-signed certificates is in local development environments. Developers often need to test applications over HTTPS on their local machine (localhost) to replicate the production environment. Generating a self-signed certificate is a fast, free way to enable TLS encryption for this purpose. Since the developer is both the creator and the sole user of the certificate, the lack of external trust is irrelevant. The goal is to test functionality, not to establish public identity.
Internal-only applications and services
Within a completely isolated corporate network (intranet), self-signed certificates can be used for internal-only services, such as administrative dashboards, internal wikis, or monitoring tools. In these cases, the organization’s IT department can manually install the self-signed certificate (or an internal root CA certificate) into the trust stores of all company-managed devices. This creates a closed-loop trust system. However, this approach requires meticulous management and is often better served by an internal CA for improved scalability and control.
Proof-of-Concept (PoC) and prototype deployment
When deploying a new application for a proof-of-concept or a very early-stage prototype, a self-signed certificate can be a temporary placeholder. It allows for the configuration and testing of TLS/SSL functionality without the overhead of purchasing a commercial certificate for a system that may be short-lived or undergo significant changes. This is acceptable as long as the PoC is not exposed to the public internet or external users who would encounter trust errors.
Isolated machine-to-machine communication
In certain Internet of Things (IoT) or backend microservices architectures, where two machines communicate over a private, isolated network, self-signed certificates can secure the communication channel. If both machines are configured to explicitly trust each other’s specific certificate (a practice known as certificate pinning), the lack of a public CA is not a security gap. This establishes a direct, pre-configured trust relationship between the two endpoints, preventing other devices from interfering.
What are the risks of using self-signed certificates?
While useful in niche scenarios, the convenience of self-signed certificates is quickly overshadowed by the vulnerabilities they create.
Browser and operating system warnings
The most immediate and obvious risk is the user experience. Every major web browser and many applications will display stark security warnings when encountering a self-signed certificate. Messages like “Your connection is not private” train users to ignore or bypass critical security alerts. This “warning fatigue” can desensitize users, making them more likely to click through a similar warning on a genuinely malicious site, neutralizing an essential security mechanism.
Lack of a centralized revocation mechanism
If the private key of a CA-signed certificate is compromised, the CA can revoke it, adding it to a Certificate Revocation List (CRL) or providing its status via the Online Certificate Status Protocol (OCSP). Browsers check this status to ensure they are not trusting a compromised certificate. Self-signed certificates have no such mechanism. If a private key is stolen, there is no way to inform clients that the certificate is no longer trustworthy, allowing an attacker to impersonate the server indefinitely until the certificate expires.
Susceptibility to man-in-the-middle (MITM) attacks
This is the most critical security risk. Self-signed SSL certificates lack publicly trusted intermediaries, making them highly susceptible to man-in-the-middle (MITM) attacks. Since clients do not trust the certificate by default, an attacker can easily intercept the connection, present their own self-signed certificate, and the user would see the exact same security warning they were trained to expect. The user has no way to distinguish the legitimate server’s untrusted certificate from the attacker’s fraudulent one, allowing the attacker to decrypt traffic, steal credentials, and inject malicious content.
Management overhead and scalability challenges
Manually managing a handful of self-signed certificates on a development server is simple. However, trying to use them at scale across an organization is a logistical nightmare. Tracking expiration dates, ensuring correct deployment, and manually establishing trust on every client device becomes unmanageable. This often leads to expired certificates causing service outages or insecure configurations being left in place.
Compliance and regulatory issues
For organizations subject to regulatory standards like PCI DSS, HIPAA, or GDPR, using self-signed certificates on systems handling sensitive data can lead to compliance failures. These standards require robust, verifiable security controls, and an untrusted, unvalidated certificate does not meet that bar. An audit that discovers self-signed certificates in a production environment could result in significant penalties and mandated remediation.
Best practices for avoiding self-signed certificates
The risks associated with self-signed certificates far outweigh their benefits in almost all production scenarios. The best practice is not to manage them better, but to create an infrastructure where they are not needed outside of development sandboxes. This involves adopting a mature, centralized approach to certificate management.
Centralize certificate management
Instead of allowing teams or individual administrators to generate certificates ad-hoc, implement a centralized certificate management platform or policy. This provides a single source of truth for all certificates within the organization. It allows security teams to have complete visibility into what certificates are deployed, who owns them, when they expire, and whether they comply with corporate policy. This prevents the “shadow IT” problem of untracked and forgotten self-signed certificates.
Automate certificate issuance and renewal
Modern certificate management relies on automation. Using protocols like ACME (Automated Certificate Management Environment) with trusted CAs (including free options like Let’s Encrypt) allows for the complete automation of the certificate lifecycle. Automated systems can handle issuance, renewal, and deployment without manual intervention, eliminating the risk of human error and expired certificates. This removes the primary motivation for using self-signed certificates—convenience—by making the secure alternative just as easy.
Continuously monitor and audit deployed certificates
You cannot secure what you cannot see. Implement continuous network scanning and monitoring tools to discover all TLS certificates in use across your environment, including internal and external-facing assets. This process will uncover any unauthorized self-signed certificates that have been deployed against policy. Regular audits ensure that all certificates are from trusted CAs, use strong cryptographic standards, and are replaced before they expire.
Educate IT teams and developers
Often, self-signed certificates are used not out of malice, but out of a lack of awareness of the risks or the available alternatives. Provide clear guidance and training to developers and IT staff on the organization’s certificate policies. Educate them on the security dangers of self-signed certificates and provide them with easy, approved workflows for obtaining trusted certificates for their projects, whether from a public CA or an internal enterprise CA.
Secure your online presence with DigiCert
Self-signed certificates are a tool of convenience, best reserved for the controlled and isolated confines of local development and internal testing. They provide a quick path to enabling encryption but critically fail to provide the authentication that underpins digital trust. When they escape these sandboxes and enter pre-production or production environments, they transform from a helpful shortcut into a significant security liability, exposing organizations to Man-in-the-Middle attacks, eroding user trust, and creating unmanageable and non-compliant infrastructure.
UltraDNS provides the authoritative DNS backbone organizations need for scale, reliability, and security. When combined with DigiCert’s certificate lifecycle management solutions, businesses can automate issuance, validation, and renewal, while ensuring DNS records propagate quickly and accurately across the internet. This synergy simplifies operations, reduces risk, and keeps digital trust intact across every connection.
Learn more about UltraDNS and how UltraDNS and DigiCert CLM work together to strengthen certificate management from the very first CSR.
