CVE-2026-103658: CWE-122 Heap-based Buffer Overflow in GNU Aspell

GNU Aspell through 0.60.8.2 contains a heap-based buffer overflow write (CWE-122) in its read-only dictionary loader. String::reserve() in common/string.hpp computes its capacity check with a signed int ((int)s + 1), so a requested size of 0x7FFFFFFF wraps negative and the backing buffer is never grown. ReadOnlyDict::load() in modules/speller/default/readonly_ws.cpp passes the unvalidated 32-bit size fields from a .rws dictionary header into this path, so a crafted .rws file with a valid endian marker (12345678) and an oversized length field (e.g. lang_name_size = 0x7FFFFFFF) causes attacker-controlled data to be written out of bounds past an undersized heap allocation. An attacker who induces a victim to load a malicious dictionary — for example via aspell dump master <file> — can corrupt heap memory, resulting in denial of service and potentially code execution. Fixed in 0.60.8.3.