AdminNeo SQLite: multi_query Incorrect Check of Function Return Value RCE

Summary

This vulnerability is a patch bypass that exploits catastrophic backtracking in a regular expression used to filter ATTACH statements in AdminNeo's SQLite functionality. The original vulnerability (CVE-2021-43008) allowed authenticated users to create PHP files through SQLite ATTACH statements, achieving remote code execution. The patch introduced a regex filter to block ATTACH queries, but this filter is vulnerable to catastrophic backtracking.

Originally reported by @zdi-disclosures in Adminer: https://github.com/vrana/adminer/security/advisories/GHSA-3582-q6xq-5vf7

Analysis

[Source] sql.inc.php :: SQL import handler:47

$query = get_file("sql_file", true, ";");

User uploads a malicious SQL file through the import form. The file content is read into the $query variable without any initial sanitization.

[Transform] sql.inc.php :: SQL import handler:87

// Query parsing loop that extracts individual SQL statements

The uploaded SQL content is processed in a loop that splits it into individual queries. Each query $query is extracted for processing.

[Context] sql.inc.php :: SQL import handler:65

$space = "(?:\\s|/\\*[\s\S]*?\\*/|(?:#|$line_comment)[^\n]*\n?|--\r?\n)";

Definition of the $space regex pattern used in the ATTACH filter. The possessive quantifier *+ combined with SQLite comment patterns (--) creates the catastrophic backtracking vulnerability when many comment lines are processed.

[Transform] sql.inc.php :: SQL import handler:146

if (DIALECT == "sqlite" && preg_match("~^$space*+ATTACH\\b~i", $q, $match)) {

The ATTACH query filter check. When the regex encounters 350,000 SQLite comment lines (--), it triggers catastrophic backtracking. The possessive quantifier *+ causes exponential backtracking, eventually hitting PHP's backtracking limit and causing preg_match() to return false instead of 0 or 1, bypassing the security filter.

[Sink] sql.inc.php :: SQL import handler:162

Connection::get()->multiQuery($q)

When the ATTACH filter is bypassed due to the preg_match() returning false, the malicious SQL query containing the ATTACH statement is executed. This allows the attacker to create a .php file with embedded PHP code, achieving remote code execution when the file is accessed via HTTP.

The root cause is that PHP's preg_match() function returns false when the backtracking limit is exceeded, but the code only checks for truthy values (1 for match), treating false the same as 0 (no match). This allows the ATTACH statement to bypass the security filter.

-- CREDIT --------------------------------------- This vulnerability was discovered by: 0daystolive (Sorcery Ltd) working with TrendAI Zero Day Initiative

Zero Day Initiative zdi-disclosures@trendmicro.com

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