IDNA decoding execution time is not linear in relation to the input string size, which can cause slowness with large inputs:
10 chars = 0.016 seconds
100 chars = 0.047 seconds
1000 chars = 2.883 seconds
2500 chars = 17.724 seconds
5000 chars = 1 min 10 seconds
According to Unicode Technical Standard #46, an IDNA label must not be longer than 63 characters. The Python idna module enforces the restriction, but too late.
Dates:
Disclosure date: 2022-10-19 (Python issue gh-98433 reported)
Reported at: 2022-09-09 (email to PSRT)
Reported by: Guido Vranken
Python 3.7.16 (2022-12-06) fixed by commit b0b590b (branch 3.7) (2022-11-08)
Python 3.8.16 (2022-12-06) fixed by commit 82ca283 (branch 3.8) (2022-11-10)
Python 3.9.16 (2022-12-06) fixed by commit c09dba5 (branch 3.9) (2022-11-10)
Python 3.10.9 (2022-12-06) fixed by commit 9bb8e18 (branch 3.10) (2022-11-08)
Python 3.11.1 (2022-12-06) fixed by commit a6f6c3a (branch 3.11) (2022-11-08)
Slow IDNA decoding with large strings [CVE-2022-45061].
Python issue: gh-98433
Creation date: 2022-10-19
Reporter: guidovranken
An issue was discovered in Python before 3.11.1. An unnecessary quadratic algorithm exists in one path when processing some inputs to the IDNA (RFC 3490) decoder, such that a crafted, unreasonably long name being presented to the decoder could lead to a CPU denial of service. Hostnames are often supplied by remote servers that could be controlled by a malicious actor; in such a scenario, they could trigger excessive CPU consumption on the client attempting to make use of an attacker-supplied supposed hostname. For example, the attack payload could be placed in the Location header of an HTTP response with status code 302. A fix is planned in 3.11.1, 3.10.9, 3.9.16, 3.8.16, and 3.7.16.
CVE ID: CVE-2022-45061
Published: 2022-11-09
Timeline using the disclosure date 2022-10-19 as reference:
2022-09-09 (-40 days): Reported (email to PSRT)
2022-10-19: Python issue gh-98433 reported by guidovranken
2022-11-08 (+20 days): commit d315722 (branch 3.12)
2022-11-08 (+20 days): commit 9bb8e18 (branch 3.10)
2022-11-08 (+20 days): commit a6f6c3a (branch 3.11)
2022-11-08 (+20 days): commit b0b590b (branch 3.7)
2022-11-09 (+21 days): CVE-2022-45061 published
2022-11-10 (+22 days): commit 82ca283 (branch 3.8)
2022-11-10 (+22 days): commit c09dba5 (branch 3.9)
2022-12-06 (+48 days): Python 3.10.9 released
2022-12-06 (+48 days): Python 3.11.1 released
2022-12-06 (+48 days): Python 3.7.16 released
2022-12-06 (+48 days): Python 3.8.16 released
2022-12-06 (+48 days): Python 3.9.16 released
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