CVE-2021-20230

NameCVE-2021-20230
DescriptionA 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.
SourceCVE (at NVD; CERT, LWN, oss-sec, fulldisc, bugtraq, EDB, Metasploit, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, Mageia, GitHub code/issues, web search, more)
NVD severitymedium
Debian Bugs982578

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
stunnel4 (PTS)stretch3:5.39-2fixed
buster3:5.50-3vulnerable
bullseye, sid3:5.56+dfsg-10fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
stunnel4sourcestretch(not affected)
stunnel4source(unstable)3:5.56+dfsg-8982578

Notes

[buster] - stunnel4 <no-dsa> (Minor issue)
[stretch] - stunnel4 <not-affected> (Re-ordering of redirect/accept/reject checks performed in stunnel 5.41b8)
https://github.com/mtrojnar/stunnel/commit/ebad9ddc4efb2635f37174c9d800d06206f1edf9
Isolated fix only the changes in src/verify.c:
https://bugzilla.suse.com/show_bug.cgi?id=1177580#c2
https://bugzilla.redhat.com/show_bug.cgi?id=1925226

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