Impact

Luxon's `DateTime.fromRFC2822() has quadratic (N^2) complexity on some specific inputs. This causes a noticeable slowdown for inputs with lengths above 10k characters. Users providing untrusted data to this method are therefore vulnerable to (Re)DoS attacks.

This is the same bug as Moment's https://github.com/moment/moment/security/advisories/GHSA-wc69-rhjr-hc9g

Workarounds

Limit the length of the input.

References

There is an excellent writeup of the same issue in Moment: https://github.com/moment/moment/pull/6015#issuecomment-1152961973

Details

DateTime.fromRFC2822("(".repeat(500000)) takes a couple minutes to complete.