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bpo-43075: Fix ReDoS in urllib AbstractBasicAuthHandler (GH-24391)

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Fix Regular Expression Denial of Service (ReDoS) vulnerability in
urllib.request.AbstractBasicAuthHandler. The ReDoS-vulnerable regex
has quadratic worst-case complexity and it allows cause a denial of
service when identifying crafted invalid RFCs. This ReDoS issue is on
the client side and needs remote attackers to control the HTTP server.
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Yeting Li 2021-04-07 19:27:41 +08:00 • committed by GitHub
parent d36d6a9c18
commit 7215d1ae25
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2 changed files with 2 additions and 1 deletions
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2
Lib/urllib/request.py
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@ -945,7 +945,7 @@ class AbstractBasicAuthHandler:
# (single quotes are a violation of the RFC, but appear in the wild)
rx = re.compile('(?:^|,)' # start of the string or ','
'[ \t]*' # optional whitespaces
'([^ \t]+)' # scheme like "Basic"
'([^ \t,]+)' # scheme like "Basic"
'[ \t]+' # mandatory whitespaces
# realm=xxx
# realm='xxx'

1
Misc/NEWS.d/next/Security/2021-01-31-05-28-14.bpo-43075.DoAXqO.rst Normal file
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@ -0,0 +1 @@
Fix Regular Expression Denial of Service (ReDoS) vulnerability in :class:`urllib.request.AbstractBasicAuthHandler`. The ReDoS-vulnerable regex has quadratic worst-case complexity and it allows cause a denial of service when identifying crafted invalid RFCs. This ReDoS issue is on the client side and needs remote attackers to control the HTTP server.