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Regular Expression Denial of Service (ReDOS)

moderate severity Published Jun 22, 2021 • Updated Jun 30, 2021

Package

npm color-string (npm)

Affected versions

< 1.5.5

Patched versions

1.5.5

Description

In the npm package color-string, there is a ReDos (Regular Expression Denial of Service) vulnerability regarding an exponential time complexity for
linearly increasing input lengths for hwb() color strings.

Strings reaching more than 5000 characters would see several
milliseconds of processing time; strings reaching more than
50,000 characters began seeing 1500ms (1.5s) of processing time.

The cause was due to a the regular expression that parses
hwb() strings - specifically, the hue value - where
the integer portion of the hue value used a 0-or-more quantifier
shortly thereafter followed by a 1-or-more quantifier.

This caused excessive backtracking and a cartesian scan,
resulting in exponential time complexity given a linear
increase in input length.

References

CVE ID

CVE-2021-29060

CVSS Score

5.3 Moderate
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L