Executive Summary

CVE-2026-36758 is a Server-Side Request Forgery (SSRF) vulnerability in Halo version 2.22.14, specifically in the /themes/-/install-from-uri endpoint.

This vulnerability allows authenticated users with ordinary privileges to send crafted HTTP GET requests to internal network addresses by exploiting the way the application fetches plugin data from user-supplied URIs without proper validation or sanitization.

The root cause is that the DefaultReactiveUrlDataBufferFetcher class does not restrict URI schemes or validate hosts, enabling attackers to scan internal resources by redirecting requests to internal services.

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Impact Analysis

This vulnerability can allow an authenticated attacker to scan and access internal network resources that are normally not exposed externally.

By sending crafted requests, attackers may gain unauthorized access to sensitive internal services and data, potentially leading to information disclosure or further exploitation within the internal network.

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Detection Guidance

This vulnerability can be detected by monitoring for unusual HTTP GET requests to the `/apis/uc.api.storage.halo.run/v1alpha1/themes/-/install-from-uri` endpoint that include user-supplied URIs targeting internal network addresses.

Since the vulnerability involves SSRF via crafted GET requests, you can look for requests that attempt to access internal IP addresses or uncommon ports such as port 6666.

Commands to detect such activity might include using network monitoring tools or web server logs to filter requests to the vulnerable endpoint and check for suspicious URI parameters.

• Use grep or similar tools on web server logs to find requests to the vulnerable endpoint, for example: `grep "/apis/uc.api.storage.halo.run/v1alpha1/themes/-/install-from-uri" /var/log/nginx/access.log`
• Use network monitoring tools like tcpdump or Wireshark to capture HTTP GET requests targeting internal IP ranges from authenticated users.
• Check for HTTP GET requests with parameters containing internal IP addresses or unusual ports (e.g., port 6666) that indicate SSRF attempts.

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Mitigation Strategies

An immediate mitigation step is to implement a blacklist that filters and blocks requests containing internal IP addresses in the user-supplied URIs.

Restrict or validate the URI schemes and hosts in requests to the `/themes/-/install-from-uri` endpoint to prevent SSRF attacks.

Ensure that only trusted and authenticated users can access this endpoint, and monitor for suspicious activity.

Consider applying any available patches or updates from the vendor that address this vulnerability.

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Compliance Impact

The CVE-2026-36758 vulnerability allows authenticated attackers to perform Server-Side Request Forgery (SSRF) attacks that can scan internal resources and potentially expose sensitive information. Such unauthorized access to internal network resources could lead to data breaches or unauthorized disclosure of personal or sensitive data.

Exposure of sensitive data or internal resources due to this vulnerability may impact compliance with data protection regulations such as GDPR or HIPAA, which require organizations to protect personal and sensitive information from unauthorized access.

However, the provided context does not explicitly mention compliance impacts or specific regulatory considerations.

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