Mmastodon TechnologySoftware first seen 11 h ago, last 9 h ago, peak #3

Tiny regex bugs that brought down Cloudflare and Stack Overflow

Original: A regular expression took Cloudflare off the internet. Another took down Stack Overflow. Both written in an afternoon, l

Developers are revisiting how short, harmless-looking regular expressions knocked major services offline. The failures stemmed from catastrophic backtracking: a repeating group nested inside another repeating group, fed input that could not match, forcing the engine to try every possible split. Cloudflare and Stack Overflow both suffered such outages, and the pattern behind them can be written in an afternoon by anyone.

Why now: Programmers are sharing a clear, cautionary explanation of catastrophic regex backtracking and famous real-world outages it caused.

CloudflareStack Overflow

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Rank over time, top of the chart is #1. 3 snapshots from 11 h ago to 9 h ago.

Evidence

• A regular expression took Cloudflare off the internet. Another took down Stack Overflow. Both written in an afternoon, looked harmless. Tiny mechanism: repeating group inside a repeating group, given input that cannot match. The engine must try every way of splitting the input… · justbits · 3

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