Executive Summary

[{'type': 'paragraph', 'content': "CVE-2026-33539 is a SQL injection vulnerability in the Parse Server's PostgreSQL adapter. It occurs because the server does not properly validate user-supplied field names in aggregate pipeline stages (specifically the $group._id field) and distinct queries. Attackers with master key access can inject SQL metacharacters such as double quotes, semicolons, or single quotes into these field names, allowing them to execute arbitrary SQL commands on the PostgreSQL database."}, {'type': 'paragraph', 'content': 'This vulnerability enables privilege escalation from an application-level administrator to database-level access, potentially allowing attackers to manipulate or damage the database.'}, {'type': 'paragraph', 'content': 'The issue affects only Parse Server deployments using PostgreSQL and has been patched by introducing strict validation of aggregate and distinct field names to reject any input containing invalid characters.'}] [1, 2]

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Impact Analysis

If you are using Parse Server with a PostgreSQL database, this vulnerability can allow an attacker who has master key access to escalate their privileges from the application level to the database level.

This means the attacker could execute arbitrary SQL commands, such as dropping tables or extracting sensitive data, which can lead to data loss, data corruption, or unauthorized data access.

MongoDB deployments of Parse Server are not affected by this vulnerability.

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Compliance Impact

I don't know

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Detection Guidance

[{'type': 'paragraph', 'content': 'This vulnerability involves SQL injection via malicious field names in aggregate ($group._id) and distinct operations in Parse Server\'s PostgreSQL adapter. Detection involves monitoring for unusual or suspicious aggregate or distinct queries containing SQL metacharacters such as double quotes (") , semicolons (;), or single quotes (\').'}, {'type': 'paragraph', 'content': 'Since the vulnerability is triggered by malformed field names in queries, detection can be done by inspecting logs or query parameters for such suspicious patterns.'}, {'type': 'list_item', 'content': 'Check Parse Server logs or database query logs for aggregate or distinct queries with field names containing characters like ", ;, or \''}, {'type': 'list_item', 'content': 'Use grep or similar tools to search logs for suspicious patterns, for example:'}, {'type': 'list_item', 'content': 'grep -E \'\\$[a-zA-Z0-9_]+"|;|\\\'\' parse-server.log'}, {'type': 'list_item', 'content': 'Monitor for Parse Server errors indicating invalid key names (e.g., Parse.Error.INVALID_KEY_NAME), which may indicate attempted exploitation.'}, {'type': 'paragraph', 'content': 'No specific detection commands are provided in the resources, but focusing on query logs and error logs for injection-like patterns is recommended.'}] [1, 3, 4]

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Mitigation Strategies

The primary mitigation is to upgrade Parse Server to a patched version where this vulnerability is fixed.

• Upgrade Parse Server to version 8.6.59 or later, or 9.6.0-alpha.53 or later, where the fix has been applied.

The fix involves strict validation of aggregate and distinct field names to ensure they only contain safe characters matching the regex pattern /^[a-zA-Z][a-zA-Z0-9_]*$/.

• Ensure that your deployment uses PostgreSQL adapter only if patched, as MongoDB deployments are not affected.

If immediate upgrade is not possible, consider restricting access to the master key or administrative interfaces to trusted users only, to reduce risk of exploitation.

Monitor logs for any suspicious aggregate or distinct queries and block or investigate them promptly.

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