KOSPI Tumbles, SK Hynix Boosts Amid Share‑Buyback Rally

South Korea’s benchmark KOSPI slipped 0.41% to 6,824.71, while the tech‑heavy KOSDAQ fell 4.74% to 800.99. The market opened lower amid broad selling, but a few stocks such as SK Hynix, Kumho Engineering & Construction and SK Securities posted strong gains on corporate news. The USD/KRW hovered at 1,391.03.

SK hynix (000660) +3.55%

SK Hynix surged 3.55% after announcing a massive 40 trillion‑won share repurchase that will be fully cancelled, triggering a sharp after‑hours rally and a more than 5 % rise on the following trading day【2】【3】【4】【5】. The move was interpreted as a confidence signal that the stock was undervalued. However, NH Securities cut its price target, reflecting a perceived correction, which may have added short‑term sell pressure【6】. An earlier headline on August 18 noted a price drop but gave no specific cause【1】.

KUMHOE&C (002990) +5.18%

Kumho Engineering & Construction jumped 5.18% as foreign and institutional investors simultaneously placed net buy orders, fueling a sharp buying surge【7】. The rally was amplified by news that Samsung Electronics will inject 240 billion won into the builder, raising expectations of future contracts and synergies【8】. The broader construction sector also enjoyed a bullish atmosphere, with many stocks posting 20 %‑plus gains, providing additional tailwinds【11】. The combined fund inflows and sector momentum explain the strong intraday performance.

SKSecurities (001510) +12.63%

SK Securities surged 12.63% after it was confirmed as the exclusive broker for SK Hynix’s 40 trillion‑won share buy‑back, a deal that could generate at least 4 billion won in fees【14】【18】. The announcement sent the stock to the daily upper‑limit and triggered a VI (price‑halt) mechanism, intensifying buying pressure【15】【17】. Market participants viewed the mandate as a lucrative, one‑off transaction, lifting sentiment toward the brokerage. The rapid price move reflects both the fee upside expectation and the technical halt that amplified demand.

DANAL CO., LTD. (064260) +4.91%

Danal rose 4.91% as a VI (volatility interruption) was triggered, automatically halting price swings and prompting a surge of buy orders from traders seeking to capture the momentum【19】【21】【22】. The rally was further supported by optimism around the U.S. “Clarity Act,” with former President Trump urging its passage, a development seen as favorable for cryptocurrency‑related firms like Danal【20】【24】. The combination of a technical halt and positive regulatory sentiment helped lift the stock despite its negative earnings and ROE.

KB Financial Group (105560) +1.50%

KB Financial Group slipped 1.5% after two consecutive days of declines—down 1.96% on August 19 and 3.85% on August 20—driven by expanding sell pressure【25】【26】. Although the August 18 earnings release highlighted a 13 % profit increase, an 18 % EPS jump and the impact of a share‑buy‑back, these fundamentals were insufficient to reverse the short‑term outflow【27】. A parallel announcement of achieving 83 % of its green‑finance target added a positive narrative, but its effect on the price remains unclear from the headlines【28】【29】.

Sources

1. SK하이닉스 주가, 오늘 하락하는 이유는? — Investing.com 한국어 · 2026-08-18
2. SK하이닉스, 40조 자사주 사들여 전량 소각…시간외 주가 급반등 — 조선일보 · 2026-08-19
3. SK하이닉스, 40조 자사주 소각 발표…NXT 애프터마켓서 5% 급등 — 연합인포맥스 · 2026-08-19
4. 배당 대신 '국내 최대' 40조 주식 소각 꺼낸 SK하이닉스…"주가 저평가 판단" — 뉴시스 · 2026-08-19
5. SK하이닉스, 40조 풀고 181조원 더?…"바닥 다진 주가, 다시 달린다" - 머니투데이 — 머니투데이 · 2026-08-20
6. NH證 "SK스퀘어, SK하이닉스 주가 조정 반영…목표가↓" — v.daum.net · 2026-08-17
7. [장중수급포착] 금호건설, 외국인/기관 동시 순매수… 주가 +30.00% — 뉴스핌 · 2026-08-20
8. 금호건설 또 주가 '상한가'...삼성전자 2400억 투입 — gukjenews.com · 2026-08-20
9. [속보] 금호건설 급등흐름 — CBC뉴스 · 2026-08-20
10. 금호건설 주가 28% 급등…상한가 문턱까지 치솟아 — 잡포스트 · 2026-08-20
11. [특징주] 금호건설, 건설업종 훈풍 속 20%대 급등세 : 한국증시 — 재경일보 · 2026-08-20
12. 금호건설 주가, 8월 19일 장중 12,740원 8.67% 하락 — 톱스타뉴스 · 2026-08-19
13. "땡큐 닉스" SK증권 주가급등…'40조 자사주 취득' 맡는다 - 머니투데이 — 머니투데이 · 2026-08-20
14. 하이닉스 자사주 매입 맡은 SK증권 상한가…수수료 최소 40억 추정 | — 연합인포맥스 · 2026-08-20
15. SK증권 주가 장중 상한가, SK하이닉스 자사주 취득 중개 소식에 우선주도 급등 — 비즈니스포스트 · 2026-08-20
16. [특징주] SK증권, 하이닉스 자사주 매입 중개 소식에 ‘상한가’ — 소년한국일보 · 2026-08-20
17. [속보] SK증권 주가, VI 발동 후 급등 — bntnews.co.kr · 2026-08-21
18. [특징주] SK증권, SK하이닉스 40조 자사주 매입 단독 중개에 '上' — 메트로신문 · 2026-08-20
19. [속보] 다날 주가 급등, VI 발동 — bntnews.co.kr · 2026-08-20
20. 트럼프, 클래리티법 법안 통과 촉구에 다날 주가 '강세' — gukjenews.com · 2026-08-20
21. [속보] 다날 VI 발동, 주가 급등 — CBC뉴스 · 2026-08-20
22. 다날 주가, 급등세... 왜? — 금강일보 · 2026-08-20
23. 다날 주가, 8월 20일 장중 5,410원 16.47% 상승 — 톱스타뉴스 · 2026-08-20
24. 우리기술투자·다날 등 가상화폐株 상승...美 클래리티법 통과 기대 — gukjenews.com · 2026-08-21
25. KB금융 주가, 8월 20일 160,000원 3.85% 하락 마감 — 톱스타뉴스 · 2026-08-20
26. KB금융 주가, 8월 19일 장중 165,200원 1.96% 하락 — 톱스타뉴스 · 2026-08-19
27. KB금융지주, 순익 13% 늘 때 EPS 18% 뛰었다…자사주 소각 효과 '본격화' — PRESS9 · 2026-08-18
28. KB금융, 자연자본금융 25조 목표 83% 달성 — 녹색경제신문 · 2026-08-18
29. KB금융 투자분석 2026. 08. 19 — 주달 · 2026-08-19

This is market commentary, not investment advice.