TimescaleDB through 2.29.1, fixed in commit 517c13e, contains an out-of-bounds read vulnerability that allows authenticated attackers to cause query-result integrity failures or backend crashes by supplying a crafted Simple8b selector-11 value, which is stored in the signed int16 Arrow dictionary-index type and bypasses index validation checks in bulk text dictionary decompression. Attackers with direct DML access to a non-frozen physical compressed hypertable relation can trigger an out-of-bounds read before the base of the live offsets array through the VectorAgg single-text hashing strategy, resulting in incorrect aggregation output, backend SIGSEGV, or PostgreSQL crash recovery depending on build configuration.