CVE-2020-13871: 
SQLite vulnerability analysis and mitigation

SQLite version 3.32.2 contains a use-after-free vulnerability in the resetAccumulator function in select.c (CVE-2020-13871). The vulnerability exists because the parse tree rewrite for window functions occurs too late in the processing sequence. This vulnerability was discovered and reported on June 5, 2020 (SQLite Ticket).

The vulnerability stems from incorrect timing of parse tree transformations required for window functions, which occurs after aggregate function analysis. This leads to a use-after-free condition in the resetAccumulator function. The issue specifically involves window function processing and aggregate function analysis timing. The vulnerability can be triggered through specially crafted SQL queries involving window functions and aggregate operations (SQLite Fix).

When successfully exploited, this vulnerability could lead to a Denial of Service (DoS) condition in applications using the affected SQLite versions. The vulnerability has been assigned a CVSS v3.1 base score of 7.5 (High) (NetApp Advisory).

The vulnerability is remotely exploitable without authentication in certain contexts. A proof of concept (PoC) exploit exists that involves a specific SQL query using window functions, GROUP BY clauses, and aggregate functions (SQLite Ticket).

The vulnerability has been fixed in SQLite versions after 3.32.2. Users should upgrade to a patched version. Multiple vendors have released patches for their products incorporating SQLite, including Debian (version 3.34.1-3), Fedora (version 3.33.0-1), and Gentoo (version >= 3.32.3) (Debian Tracker, Gentoo Advisory).