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AUSCERT External Security Bulletin Redistribution
ESB-2021.4002
Cookie Prefix Spoofing in CGI::Cookie.parse
25 November 2021
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AusCERT Security Bulletin Summary
---------------------------------
Product: Ruby
Publisher: Ruby
Operating System: UNIX variants (UNIX, Linux, OSX)
Windows
Impact/Access: Provide Misleading Information -- Remote/Unauthenticated
Reduced Security -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2021-41819 CVE-2020-8184
Reference: ESB-2021.2515
ESB-2021.1150
ESB-2020.3928
ESB-2020.3841
Original Bulletin:
https://www.ruby-lang.org/en/news/2021/11/24/cookie-prefix-spoofing-in-cgi-cookie-parse-cve-2021-41819/
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CVE-2021-41819: Cookie Prefix Spoofing in CGI::Cookie.parse
Posted by mame on 24 Nov 2021
A cookie prefix spoofing vulnerability was discovered in CGI::Cookie.parse.
This vulnerability has been assigned the CVE identifier CVE-2021-41819 . We
strongly recommend upgrading Ruby.
Details
The old versions of CGI::Cookie.parse applied URL decoding to cookie names. An
attacker could exploit this vulnerability to spoof security prefixes in cookie
names, which may be able to trick a vulnerable application.
By this fix, CGI::Cookie.parse no longer decodes cookie names. Note that this
is an incompatibility if cookie names that you are using include
non-alphanumeric characters that are URL-encoded.
This is the same issue of CVE-2020-8184 .
If you are using Ruby 2.7 or 3.0:
o Please update the cgi gem to version 0.3.1, 0.2,1, and 0.1,1 or later. You
can use gem update cgi to update it. If you are using bundler, please add
gem "cgi", ">= 0.3.1" to your Gemfile .
o Alternatively, please update Ruby to 2.7.5 or 3.0.3.
If you are using Ruby 2.6:
o Please update Ruby to 2.6.9. You cannot use gem update cgi for Ruby 2.6 or
prior.
Affected versions
o ruby 2.6.8 or prior (You can not use gem update cgi for this version.)
o cgi gem 0.1.0 or prior (which are bundled versions with Ruby 2.7 series
prior to Ruby 2.7.5)
o cgi gem 0.2.0 or prior (which are bundled versions with Ruby 3.0 series
prior to Ruby 3.0.3)
o cgi gem 0.3.0 or prior
Credits
Thanks to ooooooo_q for discovering this issue.
History
o Originally published at 2021-11-24 12:00:00 (UTC)
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