Executive Summary

[{'type': 'paragraph', 'content': 'CVE-2026-30842 is a moderate severity vulnerability in Wallos, an open-source personal subscription tracker. Before version 4.6.2, the application allowed any authenticated user to delete avatar files uploaded by other users. This happens because the avatar deletion endpoint does not properly verify that the avatar file requested for deletion belongs to the user making the request.'}, {'type': 'paragraph', 'content': "Specifically, the endpoint accepts a filename and deletes the corresponding avatar file from a shared directory after normalizing the path. However, it only checks if the requested avatar matches the current user's own avatar and fails to verify ownership of the target avatar file. Since avatar filenames are accessible to other authenticated users through the application interface or browser tools, any authenticated user who knows another user's avatar filename can delete that avatar."}, {'type': 'paragraph', 'content': 'This vulnerability is classified as CWE-862 (Missing Authorization) and was patched in Wallos version 4.6.2.'}] [1]

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Impact Analysis

This vulnerability allows any authenticated user to delete avatar files uploaded by other users, which can lead to unauthorized modification of user profile data.

While it does not impact confidentiality or availability, it affects integrity by allowing unauthorized deletion of files, potentially causing user inconvenience or disruption of user experience.

Since the attack complexity is low and no user interaction is required, an attacker with low privileges can exploit this vulnerability over the network.

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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 monitoring requests to the avatar deletion endpoint, specifically `endpoints/user/delete_avatar.php`, for deletion attempts of avatar files that do not belong to the authenticated user.'}, {'type': 'paragraph', 'content': "Since the vulnerability involves an authenticated user deleting other users' avatar files by specifying their filenames, detection can involve checking logs or network traffic for deletion requests with avatar filenames that belong to other users."}, {'type': 'paragraph', 'content': 'Commands to help detect such activity could include searching web server logs for suspicious deletion requests. For example, using grep to find deletion requests:'}, {'type': 'list_item', 'content': "grep 'delete_avatar.php' /var/log/apache2/access.log"}, {'type': 'list_item', 'content': "grep -E 'delete_avatar.php.*filename=' /var/log/apache2/access.log | grep -v 'current_user_avatar_filename'"}, {'type': 'paragraph', 'content': "Additionally, monitoring application logs or using network monitoring tools to detect unauthorized deletion attempts by comparing the avatar filenames in requests against the authenticated user's own avatar filename can help identify exploitation."}] [1]

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Mitigation Strategies

The immediate mitigation step is to upgrade Wallos to version 4.6.2 or later, where this vulnerability has been patched by adding proper authorization checks to the avatar deletion endpoint.

Until the upgrade can be performed, restrict access to the avatar deletion endpoint to trusted users only or disable the avatar deletion functionality if possible.

Additionally, monitor and audit deletion requests to detect any unauthorized attempts and inform users to avoid sharing avatar filenames unnecessarily.

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