PT-2021-13852 · Stunnel+9 · Stunnel+9
Riccardo Schirone
·
Published
2020-10-11
·
Updated
2025-08-13
·
CVE-2021-20230
CVSS v2.0
7.8
High
| Vector | AV:N/AC:L/Au:N/C:C/I:N/A:N |
Name of the Vulnerable Software and Affected Versions:
stunnel versions prior to 5.57
Description:
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.
Recommendations:
For versions prior to 5.57, update to version 5.57 or later to resolve the issue. As a temporary workaround, consider disabling the use of both redirect and verifyChain options together until a patch is available. Restrict access to the tunneled service to minimize the risk of exploitation. Avoid using the redirect option with verifyChain until the issue is resolved.
Fix
Improper Certificate Validation
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Weakness Enumeration
Related Identifiers
Affected Products
Alt Linux
Almalinux
Centos
Linuxmint
Red Hat
Red Os
Rocky Linux
Suse
Ubuntu
Stunnel