Why is SK Hynix stock plunging today?

SK Hynix Inc. stock fell 8.2% to ₩1,473,000 on Tuesday as a confluence of Chinese competitive pressure, relentless foreign selling, and a deteriorating global semiconductor sentiment pushed shares to a fifth straight session of losses.

The primary trigger was China’s ChangXin Memory Technologies (CXMT) announcing plans to launch DDR5 RDIMM server memory products built on a next-generation 4F² chip architecture by the end of 2026 — a design that packs memory cells more densely than the conventional layout and represents a direct challenge to the high-margin server memory segment that SK Hynix has dominated.

SK Hynix was also pressured by sustained foreign and retail selling in South Korean markets, with early KOSPI data showing foreign traders sold ₩5.35 billion in local stocks on Tuesday. Retail selling amounted to ₩3.72 billion.

The broader market environment compounded the damage. South Korea’s KOSPI plunged more than 5% intraday, briefly breaking below the 6,000 level and triggering a sell-sidecar circuit breaker — its sixth consecutive session of decline. Overnight, the Philadelphia Semiconductor Index had declined 2.67%, pulling U.S. memory peer Micron down as well, and that weakness carried directly into Seoul’s open.

Anticipation of Q3 earnings from chipmaking bellwethers ASML and TSMC, which are due this week, also pressured broader chip stocks.