Summary
A TLS certificate validation flaw in gopay causes its default HTTP client to accept untrusted certificates when communicating with payment provider APIs. An attacker positioned to intercept network traffic may impersonate those APIs, exposing sensitive merchant and transaction information or altering payment-related responses.
Affected context
The vulnerability occurs in gopay deployments that use the affected default client configuration for outbound payment-provider API requests. It becomes risky when network traffic can be intercepted or redirected, such as on an untrusted network, through a compromised proxy, or in an environment with manipulated routing or trust controls.
Exploit preconditions
- Attack surface: Outbound HTTPS connections from the gopay client to payment provider APIs
- Required access: A network position or infrastructure control capable of intercepting or redirecting client traffic
- Trigger point: TLS establishment performed by the default HTTP client
- Why exploitation is possible: Certificate verification is disabled, allowing an impersonating endpoint to establish a connection without proving control of the legitimate provider certificate
Why this happens
The underlying bug is a failure to enforce peer certificate validation during TLS communication. By disabling certificate verification in the default HTTP client, the application treats any presented certificate as acceptable rather than validating it against trusted authorities and the intended service identity. This behavior maps to CWE-295, Improper Certificate Validation.
Potential impact
- Attackers may read merchant credentials, request signatures, and transaction data
- Payment, refund, or order-query responses could be modified in transit
- An attacker could impersonate a payment provider API
- Transaction processing may be disrupted or redirected
- Exposed credentials or signing material could enable further account abuse
General mitigation guidance
Mitigation generally focuses on restoring secure-by-default TLS verification
and reducing trust in network-provided connection properties.
Common defensive patterns include:
- Enable certificate-chain and hostname verification for every outbound HTTPS request
- Use the platform or language runtime trust store rather than accepting arbitrary certificates
- Avoid global or default-client settings that disable TLS verification
- Keep payment-provider endpoints and trust configuration explicit and centrally managed
- Protect credentials and signatures with least privilege and minimize their exposure
- Use network segmentation, authenticated proxies, and encrypted service-to-service paths where appropriate
- Treat certificate-validation bypasses as prohibited by application security policy
How teams detect issues like this
Organizations can identify this class of issue through:
- Static analysis for disabled TLS verification, insecure transport settings, and permissive certificate callbacks
- Code review checks covering HTTP client defaults and custom TLS configuration
- Dependency and configuration scans for insecure transport behavior
- Integration tests that reject expired, mismatched, self-signed, or otherwise untrusted certificates
- Runtime monitoring for unexpected payment-provider destinations, certificate changes, or proxy interception
- Policy enforcement requiring verified TLS for payment and other sensitive outbound integrations
Automated code review and security scanning tools may help flag these patterns during development.
