CVSS 3.1
7.5 highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:NCVE-2021-20230
High (7.5) in stunnel stunnel. EPSS 1.2% chance of exploitation in the next 30 days.
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.
Severity
- EPSS
- 1.2% chance of exploitation in the next 30 days; higher than 67% of CVEs (scores of 2026-11-01)
- CWE
- CWE-295
- Published
- Modified
- Record from
- the NVD, synced
Affected
- stunnel:stunnel
References
- https://bugzilla.redhat.com/show_bug.cgi?id=1925226
- https://github.com/mtrojnar/stunnel/commit/ebad9ddc4efb2635f37174c9d800d06206f1edf9
- https://security.gentoo.org/glsa/202105-02
- https://bugzilla.redhat.com/show_bug.cgi?id=1925226
- https://github.com/mtrojnar/stunnel/commit/ebad9ddc4efb2635f37174c9d800d06206f1edf9