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[3.6] bpo-43075: Fix ReDoS in urllib AbstractBasicAuthHandler (GH-24391) #25250

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Merged
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May 6, 2021
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[3.6] bpo-43075: Fix ReDoS in urllib AbstractBasicAuthHandler (GH-24391) #25250

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2 changes: 1 addition & 1 deletion Lib/urllib/request.py
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Original file line number Diff line number Diff line change
Expand Up @@ -947,7 +947,7 @@ 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'
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Security/2021-01-31-05-28-14.bpo-43075.DoAXqO.rst
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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.