KOSPI Falls 3.65% as Samsung and SK Hynix Slide Days After Samsung's Record Quarter

Investors in Korea's memory makers are asking how long the boom lasts, not how big it is now, analysts say. Days after Samsung Electronics guided to a record quarter, the KOSPI fell 3.65% on Monday, October 12, to close at 6,384.24, its biggest one-day drop since September 2, with the two chip heavyweights leading it down, The Korea Times reports.

The numbers

• KOSPI: down 241.69 points to 6,384.24, after opening at 6,578.17. It has lost 619.50 points, or 8.85%, since October 6, falling through 7,000, 6,500 and 6,400 along the way. On September 2 it fell 3.99%.
• Kosdaq: down 4.83% to 849.19.
• Samsung Electronics fell 4.39% and SK hynix 4.52%.
• Foreign selling extended to a fourth session. The won strengthened to 1,335.1 per dollar.

All figures above are closing levels as reported by The Korea Times; intraday moves reported elsewhere were different.

Why analysts say it fell

Analysts and reports cite several causes, not all of them AI-related.

Kim Seok-hwan of Mirae Asset Securities told The Korea Times the two stocks fell "as investors weighed renewed concerns about an artificial intelligence (AI) bubble following reports about OpenAI." Those were last week's reports that OpenAI's annual revenue was lower than previously reported; The Korea Times puts the gap at $20 billion and says it "reflected different accounting methods rather than a drop in sales," noting the Nasdaq recovered 0.64% the next day. We covered the OpenAI revenue reports last week.

Invezz adds macro pressures: foreign investors sold as renewed Middle East tensions, elevated US Treasury yields and weak global semiconductor shares hit risk appetite. It quotes Kim telling Reuters that "the market's focus has shifted to whether the sharp earnings growth that started a year ago would be sustainable," and Kiwoom Securities' Han Ji-young saying, via MoneyToday, that the concern "lies not in immediate changes in memory demand." Invezz says investors are asking whether tight supply and high margins can last as the three biggest memory makers expand capacity from next year through 2028.

Earnings and prices

The selloff came after Samsung's preliminary guidance of about ₩107.4 trillion in third-quarter operating profit, which we covered last week. Prices are still rising, but more slowly: Invezz reports that TrendForce expects conventional DRAM contract prices to rise 10% to 15% quarter on quarter in the fourth quarter, compared with a roughly 60% jump in the second. Sanjeev Rana of CLSA Securities Korea told Bloomberg that "demand continues to exceed supply and HBM pricing is poised for a big step up in 2027," Invezz reports.

Yuanta Securities' Lee Jae-won told The Korea Times that Korean earnings depend largely on memory, while US leaders span a wider range of AI services and infrastructure, and cautioned against reading the gap as lost competitiveness.

The next tests are on the calendar: ASML and TSMC report this week, SK hynix on October 27, and Samsung holds its earnings call on October 29.

Limits

• The link to AI-bubble worries is one analyst's reading; the sources also cite macro factors, and no single cause is established.
• Invezz's Reuters, Bloomberg and MoneyToday quotes were read only as Invezz relays them. We did not use the stock calls Invezz publishes alongside its report.

Sources

• The Korea Times: KOSPI plunges 3.65% despite Samsung's record earnings (October 12, 2026)
• Invezz: Why are Samsung and SK Hynix crashing even as memory prices keep climbing? (October 12, 2026)
• Times of AI: OpenAI annualized revenue reports
• Times of AI: Samsung Guides to ₩107.4 Trillion Quarterly Profit as Analysts Credit AI Memory