Bug 1925226 (CVE-2021-20230) - CVE-2021-20230 stunnel: client certificate not correctly verified when redirect and verifyChain options are used
Summary: CVE-2021-20230 stunnel: client certificate not correctly verified when redire...
Alias: CVE-2021-20230
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
Depends On: 1925229 1925230 1926897 1926894 1926895 1926896
Blocks: 1919806 1926224
TreeView+ depends on / blocked
Reported: 2021-02-04 16:15 UTC by Riccardo Schirone
Modified: 2021-02-23 14:09 UTC (History)
8 users (show)

Fixed In Version: stunnel 5.57
Doc Type: If docs needed, set a value
Doc Text:
A flaw was found in stunnel, where it improperly validates client certificates when it is configured to use both redirect and verifyChain options. This flaw allows an attacker with a certificate signed by a Certificate Authority, which is not the one accepted by the stunnel server, to access the tunneled service instead of being redirected to the address specified in the redirect option. The highest threat from this vulnerability is to confidentiality.
Clone Of:
Last Closed: 2021-02-22 13:02:02 UTC

Attachments (Terms of Use)

System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2021:0618 0 None None None 2021-02-22 10:26:47 UTC
Red Hat Product Errata RHSA-2021:0619 0 None None None 2021-02-22 10:39:54 UTC
Red Hat Product Errata RHSA-2021:0620 0 None None None 2021-02-22 10:26:02 UTC

Description Riccardo Schirone 2021-02-04 16:15:34 UTC
stunnel before version 5.57 does not correctly verify the client certificate when options `redirect` and `verifyChain` are used. `redirect` redirects TLS client connections to another address when there is a certificate-based authentication failure and `verifyChain` is used to verify the client certificate starting from the root CA (specified in CAfile or CApath). When these options are used together, the stunnel server does not correctly validate the client certificate, allowing a client with a certificate not signed by the right CA to access the service without being redirected to the specified `redirect` address.

Upstream 5.57 release patch:

Comment 2 Riccardo Schirone 2021-02-04 16:58:14 UTC
"redirect" option was added in stunnel upstream version 5.00, according to https://www.stunnel.org/NEWS.html .

Comment 9 RaTasha Tillery-Smith 2021-02-09 17:04:21 UTC

This issue did not affect the versions of stunnel as shipped with Red Hat Enterprise Linux 5, 6, and 7 as they did not include support for the "redirect" option.

Comment 13 errata-xmlrpc 2021-02-22 10:25:59 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.1 Extended Update Support

Via RHSA-2021:0620 https://access.redhat.com/errata/RHSA-2021:0620

Comment 14 errata-xmlrpc 2021-02-22 10:26:45 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2021:0618 https://access.redhat.com/errata/RHSA-2021:0618

Comment 15 errata-xmlrpc 2021-02-22 10:39:51 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.2 Extended Update Support

Via RHSA-2021:0619 https://access.redhat.com/errata/RHSA-2021:0619

Comment 16 Product Security DevOps Team 2021-02-22 13:02:02 UTC
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):


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