[New-bugs-announce] [issue46707] Parser hanging on stacked { tokens

[anthony shaw]

New submission from anthony shaw <anthonyshaw at apache.org>:

Providing an (invalid) input to the parser causes an exponentially-slow DoS to the Python executable in 3.10.

e.g.

python3.10 -c "{{{{{{{{{{{{{{{{{{{{{:"

takes ~2 seconds

python3.10 -c "{{{{{{{{{{{{{{{{{{{{{{{{:"

takes ~22 seconds

Tested this all the way up to 
d{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{```{{{{{{{ef f():y

which took over an hour

----------
components: Parser
keywords: 3.10regression
messages: 412972
nosy: anthonypjshaw, lys.nikolaou, pablogsal
priority: normal
severity: normal
status: open
title: Parser hanging on stacked { tokens
type: crash

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue46707>
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