High severity7.5NVD Advisory· Published Feb 23, 2021· Updated Jun 17, 2026
CVE-2021-20230
CVE-2021-20230
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.
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Affected products
19- osv-coords16 versionspkg:rpm/almalinux/stunnelpkg:rpm/opensuse/stunnel&distro=openSUSE%20Leap%2015.2pkg:rpm/suse/stunnel&distro=SUSE%20Enterprise%20Storage%206pkg:rpm/suse/stunnel&distro=SUSE%20Linux%20Enterprise%20High%20Performance%20Computing%2015%20SP1-ESPOSpkg:rpm/suse/stunnel&distro=SUSE%20Linux%20Enterprise%20High%20Performance%20Computing%2015%20SP1-LTSSpkg:rpm/suse/stunnel&distro=SUSE%20Linux%20Enterprise%20High%20Performance%20Computing%2015-ESPOSpkg:rpm/suse/stunnel&distro=SUSE%20Linux%20Enterprise%20High%20Performance%20Computing%2015-LTSSpkg:rpm/suse/stunnel&distro=SUSE%20Linux%20Enterprise%20Module%20for%20Server%20Applications%2015%20SP2pkg:rpm/suse/stunnel&distro=SUSE%20Linux%20Enterprise%20Server%2015%20SP1-BCLpkg:rpm/suse/stunnel&distro=SUSE%20Linux%20Enterprise%20Server%2015%20SP1-LTSSpkg:rpm/suse/stunnel&distro=SUSE%20Linux%20Enterprise%20Server%2015-LTSSpkg:rpm/suse/stunnel&distro=SUSE%20Linux%20Enterprise%20Server%20for%20SAP%20Applications%2015pkg:rpm/suse/stunnel&distro=SUSE%20Linux%20Enterprise%20Server%20for%20SAP%20Applications%2015%20SP1pkg:rpm/suse/stunnel&distro=SUSE%20Manager%20Proxy%204.0pkg:rpm/suse/stunnel&distro=SUSE%20Manager%20Retail%20Branch%20Server%204.0pkg:rpm/suse/stunnel&distro=SUSE%20Manager%20Server%204.0
< 5.56-5.el8_3+ 15 more
- (no CPE)range: < 5.56-5.el8_3
- (no CPE)range: < 5.57-lp152.2.6.1
- (no CPE)range: < 5.44-3.8.1
- (no CPE)range: < 5.44-3.8.1
- (no CPE)range: < 5.44-3.8.1
- (no CPE)range: < 5.44-3.8.1
- (no CPE)range: < 5.44-3.8.1
- (no CPE)range: < 5.57-3.11.1
- (no CPE)range: < 5.44-3.8.1
- (no CPE)range: < 5.44-3.8.1
- (no CPE)range: < 5.44-3.8.1
- (no CPE)range: < 5.44-3.8.1
- (no CPE)range: < 5.44-3.8.1
- (no CPE)range: < 5.44-3.8.1
- (no CPE)range: < 5.44-3.8.1
- (no CPE)range: < 5.44-3.8.1
Patches
Vulnerability mechanics
References
3- github.com/mtrojnar/stunnel/commit/ebad9ddc4efb2635f37174c9d800d06206f1edf9nvdPatchThird Party Advisory
- bugzilla.redhat.com/show_bug.cginvdIssue TrackingThird Party Advisory
- security.gentoo.org/glsa/202105-02nvdThird Party Advisory
News mentions
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