Executive Summary

CVE-2025-70886 is a persistent denial-of-service (DoS) vulnerability in Halo CMS version 2.22.4 and earlier. It allows a remote attacker to crash the administrator comment interface by submitting malformed comment payloads to the public comment submission endpoint.

Specifically, attackers send crafted comments missing required fields such as the subjectRef.version field. These malformed comments are stored in the system and cause an unhandled exception when the admin comment page attempts to read or render them, resulting in an internal server error (HTTP 500).

This causes the backend comment management page to become inaccessible, effectively causing a persistent denial of service on the comment administration interface until the offending comments are manually removed or fixed.

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Impact Analysis

The vulnerability can cause the administrator comment management page in Halo CMS to become unavailable due to a persistent denial of service condition.

This means that administrators will be unable to access or manage comments through the admin interface, potentially disrupting moderation and management workflows.

Recovery from this condition typically requires manual intervention, such as deleting the malicious comments from the database or using plugins like Data Studio to remove them.

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Compliance Impact

I don't know

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Detection Guidance

[{'type': 'paragraph', 'content': 'This vulnerability can be detected by sending crafted malformed comment payloads to the public comment submission endpoint of Halo CMS and observing the response and behavior of the admin comment interface.'}, {'type': 'paragraph', 'content': 'A practical detection method involves using the provided Proof-of-Concept (PoC) scripts that send POST requests with JSON payloads missing the required field `subjectRef.version` to the endpoint `/apis/api.halo.run/v1alpha1/comments`. If the admin comment page returns an HTTP 500 Internal Server Error or becomes inaccessible, the system is vulnerable.'}, {'type': 'paragraph', 'content': 'Manual detection steps include:'}, {'type': 'list_item', 'content': 'Clone the PoC repository from GitHub.'}, {'type': 'list_item', 'content': 'Deploy a Halo CMS instance version 2.22.4 or earlier.'}, {'type': 'list_item', 'content': 'Configure the comment system to allow comments from unregistered users and enable comments.'}, {'type': 'list_item', 'content': 'Use Node.js or similar tools to send a POST request with a malformed JSON payload missing the `subjectRef.version` field to the comment API endpoint.'}, {'type': 'list_item', 'content': 'Access the admin comment page and check for HTTP 500 errors or failure to load.'}, {'type': 'paragraph', 'content': 'Example command using curl (adjust URL and payload accordingly):'}, {'type': 'list_item', 'content': 'curl -X POST https://your-halo-instance/apis/api.halo.run/v1alpha1/comments -H "Content-Type: application/json" -d \'{"comment":"test","subjectRef":{}}\''}, {'type': 'paragraph', 'content': 'If the admin comment page crashes or returns an internal server error after submitting such a payload, the vulnerability is present.'}] [1, 2]

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Mitigation Strategies

Immediate mitigation steps include:

• Use the Data Studio plugin or equivalent administrative tools to manually delete any malicious or malformed comments that cause the admin comment interface to crash.
• Restrict or disable public comment submissions temporarily to prevent attackers from submitting malformed payloads.
• Implement server-side validation or filtering to reject comments missing required fields such as `subjectRef.version`.
• Monitor the admin comment page for errors and remove offending comments from the database manually if necessary.

Note that as of the latest information, no official patch is available, so these steps serve as temporary workarounds to maintain availability of the admin comment interface.

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