CVE-2026-121007 in SQL::Abstract
Summary
by MITRE • 11/04/2026
SQL::Abstract versions from 1.90_01 before 2.000001_04 for Perl allow SQL injection via the where values of a nested statement in an identifier position.
A nested statement such as { -select => ... } in a position where plain scalars are identifiers treats its own plain scalars as identifiers too. These positions are the select list, ORDER BY, GROUP BY, RETURNING, and with the ExtraClauses plugin FROM (-as) and JOIN (to). The values of the statement's where, having and set clauses, and the rows of a -values, go into the SQL text instead of the bind list, unescaped unless quote_char is set. Subselects in a WHERE condition are not affected.
An application that passes untrusted input as a where value of such a nested statement, expecting it to be bound, allows SQL injection.
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Analysis
by VulDB Data Team • 11/04/2026
The vulnerability identified in Perl's SQL::Abstract library represents a critical flaw in how the module handles identifier quoting for subqueries and nested statements. Versions ranging from 1.90_01 up to but not including 2.000001_04 are susceptible because they fail to properly escape or bind values that appear as identifiers within specific clauses of a nested SQL statement. In standard database interaction patterns, user-supplied data intended for filtering conditions should be passed through parameterized queries where the value is bound separately from the query structure. However, in this library's implementation, when a developer uses a hash reference to define a subquery using keys such as -select, the module incorrectly treats certain scalar values within that nested context as literal SQL identifiers rather than bindable parameters. This misclassification occurs specifically in positions where plain scalars are expected to function as column names or table aliases, including the select list, ORDER BY clauses, GROUP BY clauses, RETURNING statements, and when utilizing the ExtraClauses plugin for FROM and JOIN operations via the -as and to keys respectively.
The technical root cause lies in the parsing logic of the library which determines whether a value should be quoted as an identifier or added directly into the SQL string as part of the WHERE, HAVING, SET clauses, or VALUES rows within that nested statement. If the quote_char configuration is not explicitly set by the application developer, these values are inserted unescaped directly into the generated SQL text. This behavior creates a direct path for SQL injection attacks if an attacker can control any input passed as a value in these specific identifier positions of a subquery. It is important to note that this vulnerability does not affect standard WHERE conditions involving subqueries where the logic remains intact, but it specifically targets the structural components like ordering and grouping within nested selects. An application developer might reasonably assume that passing untrusted user input into such a structure would result in safe binding, leading to a false sense of security while leaving the database backend exposed to malicious SQL execution.
The operational impact of this vulnerability is severe, as it allows remote attackers or local users with access to vulnerable functions to execute arbitrary SQL commands on the underlying database server. By injecting crafted payloads into fields such as ORDER BY columns or GROUP BY expressions within a subquery, an attacker can bypass authentication mechanisms, extract sensitive data from other tables via UNION-based injection techniques, modify or delete existing records, and potentially gain control over the operating system if the database service has elevated privileges. This flaw undermines the primary defense mechanism against SQL injection, which is input validation through parameterization, because the library fails to distinguish between structural identifiers and dynamic values in these specific contexts. The risk is particularly high for applications that dynamically generate sorting or grouping criteria based on user preferences without rigorous server-side validation of allowed column names.
To mitigate this vulnerability, organizations must upgrade SQL::Abstract to version 2.000001_04 or later where the issue has been resolved by correcting the identifier quoting logic in nested statements. For applications that cannot immediately update their dependencies due to compatibility constraints, a robust workaround involves explicitly setting the quote_char configuration option within the SQL::Abstract instance before executing queries involving subqueries with dynamic identifiers. This forces the library to treat all scalar values as quoted identifiers regardless of their position, thereby neutralizing the injection vector. Additionally, developers should implement strict allow-listing for any user-supplied column names used in ORDER BY or GROUP BY clauses rather than relying solely on escaping mechanisms. Regular security audits and static code analysis tools configured to detect SQL::Abstract usage patterns can help identify instances where untrusted data is passed into these vulnerable structures before they are deployed into production environments. This incident highlights the importance of verifying how third-party database abstraction layers handle edge cases in query construction, particularly when dealing with complex nested queries that deviate from simple SELECT statements.