High severity · published Feb 23, 2021
CVE-2021-20230
A flaw was found in stunnel before 5.57, where it improperly validates client certificates when it is configured to use both redirect and verifyChain options
7.5
CVSS
1.2%
EPSS
No
On KEV
Description
A flaw was found in stunnel before 5.57, 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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)1.2% · higher than 68% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
ST
Stunnel · Stunnel
before 5.57 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-20230
CVE.org
https://www.cve.org/CVERecord?id=CVE-2021-20230
Issue Tracking
https://bugzilla.redhat.com/show_bug.cgi?id=1925226
Patch
https://github.com/mtrojnar/stunnel/commit/ebad9ddc4efb2635f37174c9d800d06206f1edf9
Third Party Advisory
https://security.gentoo.org/glsa/202105-02
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