Cloudflare Regex Outage

The CPU exhaustion was caused by a single WAF rule that contained a poorly written regular expression that ended up creating excessive backtracking. The regular expression that was at the heart of the outage is (?:(?:"|'|`|\||\\|\}|\]|\d (?:nan|infinity|true|false|null|undefined|symbol|math)|\`|\- |\+)+])*;?((?:\s|-|~|!|{}|\\|\+)*.*(?:.*=.*)))

A screenshot shows a technical explanation of a Cloudflare outage caused by a poorly written regular expression that triggered excessive backtracking. The joke is that the supposedly simple WAF rule is followed by an intimidating, extremely complex regex, making the incident feel absurdly difficult to understand and the probabilities dangerous to multiply. It can be sent as a reaction to overcomplicated code, catastrophic bugs, or postmortems with an overwhelming list of causes.

• @ithueti / 1074 2019-07-13