CVE-2025-14087: Glib: glib: buffer underflow in gvariant parser leads to heap corruption

A buffer-underflow vulnerability exists in GLib’s GVariant parser, specifically within bytestringparse() and stringparse(). The parser uses signed 32-bit integers (gint) as loop indices (i and j). When extremely large strings are parsed, these counters overflow into negative values, causing the parser to write to memory before the start of the allocated buffer (str[j++]). This results in a classic out-of-bounds write condition. Because GVariant parsing is often performed on attacker-influenced data, a remote attacker can trigger heap corruption, causing a crash or potentially achieving code execution. This flaw has been confirmed by maintainers and patched upstream.