Insecure TLS Verification in Coder AI Bridge Proxy

Executive Summary

This vulnerability, identified as CVE-2026-55436, affects the AI Bridge Proxy component of the Coder platform versions 2.30.0 up to but not including 2.32.7, 2.33.8, and 2.34.2. The issue arises because the proxy's default transport configuration sets `InsecureSkipVerify: true` when no upstream proxy is configured. This means that outbound HTTPS connections from the AI Bridge Proxy to the Coder access URL do not verify TLS certificates, allowing a man-in-the-middle attacker positioned between the proxy and the Coder server to intercept and potentially manipulate sensitive data.

The vulnerability does not affect deployments where the proxy and server are co-located over loopback, as the network path is secure in that scenario. The problem was fixed in later versions by enforcing secure TLS transport (TLS 1.2 or higher with system root CAs) unconditionally, regardless of upstream proxy configuration.

Workarounds include ensuring the Coder access URL uses a trusted certificate and securing the network path between the AI Bridge Proxy and the Coder server, for example by using loopback or mutual TLS (mTLS).

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Impact Analysis

This vulnerability can lead to a man-in-the-middle attack where an attacker intercepts outbound HTTPS traffic from the AI Bridge Proxy to the Coder server without proper TLS certificate verification.

• Exposure of sensitive data such as Coder session tokens.
• Leakage of user-supplied provider API keys.
• Interception of full request and response bodies, including prompts and completions.

Because the vulnerability allows interception and potential manipulation of confidential and integrity-sensitive data without requiring privileges or user interaction, it poses a high security risk.

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Detection Guidance

Detection of this vulnerability involves verifying whether the AI Bridge Proxy (aibridgeproxyd) in your Coder deployment is using insecure TLS settings, specifically if the transport has InsecureSkipVerify set to true when no upstream proxy is configured.

You can check the version of the Coder AI Bridge Proxy to see if it is within the vulnerable range (versions 2.30.0 up to but not including 2.32.7, 2.33.8, or 2.34.2).

Additionally, you can inspect the proxy's TLS configuration or network traffic to detect if TLS certificate verification is being skipped.

• Check the running version of the AI Bridge Proxy binary or container image.
• Use network monitoring tools (e.g., tcpdump, Wireshark) to capture traffic between the AI Bridge Proxy and the Coder server and analyze if TLS handshakes are properly validated.
• Run commands to inspect environment variables and proxy settings, for example:
• - `ps aux | grep aibridgeproxyd` to check process arguments and environment.
• - `env | grep -i proxy` to see if HTTP_PROXY or HTTPS_PROXY variables are set.
• - Review configuration files or logs for indications of TLS verification being disabled.

Note that the fix introduced a test named TestProxy_AIBridgeTLSVerification to validate TLS verification paths, which could be adapted or referenced for detection.

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Mitigation Strategies

To mitigate this vulnerability immediately, you should upgrade the AI Bridge Proxy component of Coder to one of the fixed versions: 2.32.7, 2.33.8, or 2.34.2 or later.

If upgrading is not immediately possible, apply the following workarounds:

• Ensure the Coder access URL uses a trusted TLS certificate.
• Secure the network path between the AI Bridge Proxy and the Coder server, for example by co-locating them over loopback or using mutual TLS (mTLS).

Be aware that the fix enforces secure TLS transport unconditionally, which may cause HTTPS deployments using private CAs not in the system trust store to fail. In such cases, you will need to add the private CA certificates to the system trust store.

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Compliance Impact

This vulnerability allows a man-in-the-middle attacker to intercept sensitive data such as session tokens, user-supplied API keys, and full request/response bodies. Such exposure of confidential information can lead to violations of data protection regulations like GDPR and HIPAA, which require the protection of personal and sensitive data in transit.

Because the vulnerability involves skipping TLS certificate verification, it undermines the confidentiality and integrity of data communications, potentially leading to unauthorized data disclosure. Organizations using affected versions without proper mitigation may fail to meet compliance requirements for secure data transmission.

Mitigations such as applying the fixed versions, using trusted certificates, and securing the network path (e.g., loopback or mTLS) are necessary to restore compliance with these standards.

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