CVE-2026-101110 in Book Library Extension
Summary
by MITRE • 09/28/2026
Joomla Extension - ordasoft.com - Unauthenticated SQL Injection in Book Library (Free) < 6.4.6 - site/booklibrary.php’s books() function reads the field and direction request parameters and passes each through a function called protectInjectionWithoutQuote(), whose only real protection is a keyword blacklist that, on detecting the literal substring select, wraps the value in $db->quote() instead of rejecting it. The value is then concatenated directly into an unquoted ORDER BY clause, a position where quoting provides no protection at all. Reaching the vulnerable code path requires two conditions: a first request to prime session-stored sort defaults, and a trailing decoy comment (-- xselect) that satisfies the blacklist’s substring check without altering the payload’s effect.
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Analysis
by VulDB Data Team • 09/28/2026
The vulnerability identified in Joomla Extension Book Library versions prior to 6.4.6 represents a critical unauthenticated SQL injection flaw located within the site/booklibrary.php script, specifically affecting the books() function. This component is widely used for managing and displaying library collections on Joomla-based websites, making its compromise potentially impactful across numerous installations. The core technical failure stems from how user-supplied input parameters, namely field and direction, are processed before being incorporated into database queries. Instead of employing parameterized queries or robust validation mechanisms that reject invalid characters entirely, the application relies on a flawed sanitization routine known as protectInjectionWithoutQuote(). This function operates by maintaining a static blacklist of keywords intended to block common SQL injection patterns. However, this approach is fundamentally insecure because it attempts to filter malicious syntax rather than validate expected input formats, creating numerous opportunities for evasion through encoding variations or logical bypasses that are well-documented in vulnerability research literature.
The specific mechanism of exploitation involves the concatenation of these sanitized parameters directly into an unquoted ORDER BY clause within a SQL statement. In standard Structured Query Language execution contexts, quoting identifiers such as column names is not only unnecessary but often syntactically incorrect when used inside order by clauses depending on the database engine's strictness. More critically, even if quotes were applied correctly to protect against injection in other parts of a query, they offer zero protection within an ORDER BY clause because SQL interprets quoted strings as literal values rather than column identifiers or sort directions. Consequently, any malicious payload injected into these parameters is executed directly by the database engine without being neutralized by string escaping mechanisms. This architectural decision renders the blacklist-based filtering ineffective for this specific code path, allowing attackers to manipulate the query structure itself rather than just its data content.
Exploiting this vulnerability requires a two-step process that leverages session state and keyword evasion techniques. First, an attacker must send an initial request to prime the session-stored sort defaults, establishing a baseline context within the application's memory for subsequent interactions. Following this initialization phase, the actual injection payload is delivered using a trailing decoy comment syntax, specifically formatted as -- xselect. This technique exploits the logic of the protectInjectionWithoutQuote() function by ensuring that the literal substring select appears in the input string. The presence of this keyword triggers the function's protective measure, which wraps the value in database quoting functions. However, because the injection occurs within an ORDER BY clause where quotes do not prevent execution of injected SQL commands, and due to the way comments are parsed by most relational databases, the quoted portion is effectively ignored or treated as part of a larger syntactic structure that allows the malicious code to execute. The -- xselect construct ensures the blacklist check passes while preserving the functional integrity of the injection payload, demonstrating a sophisticated understanding of both PHP application logic and SQL parsing rules.
The operational impact of this unauthenticated SQL injection is severe, granting remote attackers the ability to read arbitrary data from the Joomla database without any form of authentication or user interaction beyond accessing specific URLs. Depending on the configuration of the underlying MySQL or MariaDB server, an attacker could potentially extract sensitive information such as administrator usernames and password hashes, access private content stored in other tables, or even escalate privileges if certain file system permissions are misconfigured. This aligns with CWE-89 Improper Neutralization of Special Elements used in an SQL Command, highlighting the failure to properly sanitize user input before its use in a database query. Furthermore, from a tactical perspective, this vulnerability maps directly to MITRE ATT&CK technique T1059.004 Command and Scripting Interpreter: SQL Commands, as it allows for direct execution of structured queries against the backend data store. The lack of authentication requirements places this flaw in the highest severity category regarding accessibility, meaning any internet-facing Joomla site running a vulnerable version is immediately exploitable by automated scanning tools or malicious actors seeking to compromise web applications.
Mitigation strategies must prioritize immediate remediation through software updates and defensive coding practices. The most effective solution is to upgrade the Book Library extension to version 6.4.6 or later, where this vulnerability has been addressed by developers who likely replaced the fragile blacklist approach with parameterized queries or strict input validation that rejects any non-alphanumeric characters in sort fields. For organizations unable to patch immediately due to compatibility constraints, a temporary workaround involves implementing a Web Application Firewall rule set designed to detect and block SQL injection patterns within ORDER BY clauses, particularly those involving comment-based bypasses like -- xselect. Additionally, database-level security controls such as restricting the permissions of the web application's database user account can limit the blast radius in case an exploit succeeds. It is crucial for administrators to audit their Joomla extensions regularly and ensure that all components are kept up-to-date with the latest security releases provided by vendors, as legacy code often contains these types of structural flaws that become trivially exploitable once known patterns like keyword blacklisting are understood by attackers.