Euronext said its 19 October 2020 trading disruption was caused by a technical fault in third-party middleware and “was not related to a cyber-attack.” That is the exchange operator’s stated finding; the available statements do not establish an independent forensic conclusion.
What caused the Euronext trading halt?
In a notice published on 20 October 2020, Euronext attributed the disruption to “a technical issue affecting a third-party middleware system in charge of managing the persistence of data,” and said it was not related to a cyber-attack. Euronext said it had identified and resolved the issue. Euronext’s market-status notice is the primary source for that explanation.
In contemporaneous coverage, AFP quoted an unnamed Euronext spokesperson saying, “It was not a cyber attack,” and describing a technical problem resolved at the middleware level. The spokesperson was not named. SecurityWeek’s AFP report provides that additional contemporaneous account.
When did trading stop, and what happened at the close?
| Time on 19 October 2020 | What Euronext reported |
|---|---|
| 09:48 CEST | Trading halted on Euronext’s cash and derivatives segments, except Oslo Børs, according to Euronext’s 20 October notice. |
| After 17:30 CEST | Trading continued during the pre-auction. Euronext said some orders that should not have executed in that phase did execute, causing sudden share-price movements in some cases and leaving some closing prices inaccurate, according to its 20 October notice. |
The morning halt and the later closing-process disruption were separate effects reported during the same day. The explanation Euronext gave for the underlying fault was the third-party middleware issue; the post-17:30 CEST executions and price corrections were consequences for market operations.
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What did Euronext do about affected trades and prices?
Euronext said it cancelled trades performed after 17:30 CEST, with an exception for commodities, and reset order books for all Euronext instruments. It also said the applicable trading rules required closing prices to be updated to the last executed price. The operator published corrected closing values for five main indices for 19 October 2020:
| Index | Corrected close on 19 October 2020 |
|---|---|
| PSI20 | 4,214.10 |
| AEX | 567.52 |
| ISEQ20 | 1,162.82 |
| CAC40 | 4,942.62 |
| BEL20 | 3,262.38 |
These are Euronext’s corrected historical closes for that date, not current index levels. Its market-status notice contains the operator’s account of the cancellations, order-book reset, and corrected prices.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Was the next trading session affected?
Euronext said it was in a position to secure a smooth market opening on 20 October 2020. The operator apologized for the inconvenience and said it had taken actions to reduce the chance of recurrence. Those statements describe Euronext’s assessment and response; they do not, by themselves, establish the results of an independent review.
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