Patch phpMyFAQ Immediately to Fix Critical SQL Injection in Autocomplete API
Unauthenticated attackers can exploit CVE-2026-109573 in phpMyFAQ versions prior to 4.1.9 to steal credentials and modify database records through a flawed escape mechanism.
Key points
- The National Vulnerability Database rates CVE-2026-109573 as a critical flaw with a CVSS score of 9.2.
- The vulnerability exists in the PdoMysql::escape() function, which fails to properly sanitize input when databases use NO_BACKSLASH_ESCAPES mode.
- Attackers do not need credentials to exploit this issue, allowing them to read secrets, alter data, or drop tables via the api/autocomplete endpoint.
phpMyFAQ, a widely used open-source knowledge base system, contains a critical SQL injection vulnerability identified as CVE-2026-109573. According to the National Vulnerability Database record, this flaw allows unauthenticated attackers to execute arbitrary SQL commands. The issue stems from how the application handles character escaping within its database interaction layer, specifically affecting versions released before 4.1.9 and before 4.2.0-beta. This exposure poses a severe risk to any installation that has not yet applied the necessary security updates.
Root cause
The technical root of this vulnerability lies in the PdoMysql::escape() function within the phpMyFAQ codebase. This function is responsible for sanitizing user input before it is sent to the database. However, it escapes single quotes using backslashes, a method that becomes insecure when MySQL or MariaDB is configured to run in NO_BACKSLASH_ESCAPES mode. In this specific database configuration, backslashes are treated as literal characters rather than escape indicators. Consequently, the intended protection fails, leaving the underlying SQL queries open to manipulation. This weakness is classified under CWE-89, which covers SQL injection flaws.
Attack path
An attacker can exploit this flaw without needing any valid user credentials or session tokens. The attack vector targets the search parameter of the api/autocomplete endpoint. According to the NVD description, the attacker sends a Unicode right single quotation mark in this parameter. The application normalizes this Unicode character into a standard ASCII quote. Because the PdoMysql::escape() function fails to handle this normalized input correctly in the specified database mode, the quote breaks out of the intended string context. This allows the attacker to append malicious SQL commands to the original query.
Successful exploitation enables the attacker to read sensitive data, including user credentials and configuration secrets stored in the database. Beyond data theft, the vulnerability permits modification of existing records and the ability to drop entire tables. These actions can lead to complete data loss or persistent unauthorized access within the knowledge base system. The critical nature of these capabilities is reflected in the high CVSS score assigned by the National Vulnerability Database.
Affected versions
The vulnerability affects specific releases of the phpMyFAQ software developed by Thorsten. Administrators must verify their current version against the following ranges to determine exposure:
- phpMyFAQ versions prior to 4.1.9 are vulnerable to this SQL injection flaw.
- phpMyFAQ versions prior to 4.2.0-beta are also affected and require immediate attention.
- Any installation running these older builds is at risk unless the database configuration prevents the specific escape failure.
Mitigation
The primary mitigation strategy is to update the phpMyFAQ installation to a patched version. Administrators should verify that their software is at least version 4.1.9 or a stable release equal to or higher than 4.2.0. If immediate updating is not possible, reviewing the database configuration for the NO_BACKSLASH_ESCAPES mode may help, though this does not guarantee full protection against all attack vectors. Monitoring logs for unusual activity in the api/autocomplete endpoint is also advisable.
Background: Unauthorized access
Stop unauthorized access by enforcing strict identity verification, minimizing the data surface available to attackers, and continuously monitoring system integrity. This checklist covers identity controls, data protection, and network segmentation to reduce the risk of intrusions.
Read the full guide: Unauthorized Access Prevention Checklist for Systems
What to do and how to stay safe: phpMyFAQ
- Check your phpMyFAQ version immediately and upgrade to 4.1.9 or later if you are running an older build.
- Review your MySQL or MariaDB configuration to see if NO_BACKSLASH_ESCAPES is enabled, as this mode triggers the specific escape failure.
- Monitor server logs for unusual traffic targeting the api/autocomplete endpoint, which could indicate an ongoing exploitation attempt.
- Ensure that database accounts used by the application have the minimum necessary permissions to limit the impact of any successful injection.
Step-by-step guide: Vulnerability Management Definition and Process
General security guidance from the DarkWeb Headlines newsroom. It is not confirmed advice from the organisations named in this story.
Frequently asked questions
What is the CVSS score for CVE-2026-109573?
The National Vulnerability Database assigns a CVSS score of 9.2 to this vulnerability, rating it as critical.
Does an attacker need a login to exploit this flaw?
No, the vulnerability allows unauthenticated attackers to execute SQL commands without needing valid credentials.
Which specific function in phpMyFAQ is responsible for this issue?
The PdoMysql::escape() function contains the flaw that leads to improper handling of quote characters.
