CVE catalog
CVE-2021-20230
stunnel4: CVE-2021-20230
- Severity
- High · CVSS 7.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - Published
- Source
- [NVD] · [CVE record]
- EPSS
- 1.18% · Oct 25, 2026
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.
Vulnerable and fixed packages
Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.
| Distribution | Package | Release | Version | Status |
|---|---|---|---|---|
| Debian | stunnel4 | trixie | 3:5.74-2 | fixed |
| Debian | stunnel4 | bookworm | 3:5.68-2+deb12u1 | fixed |
| Ubuntu | stunnel4 | pro | 3:5.39-2 | vulnerable |
| Ubuntu | stunnel4 | pro | 3:5.42-1 | vulnerable |
| Ubuntu | stunnel4 | pro | 3:5.44-1ubuntu1 | vulnerable |
| Ubuntu | stunnel4 | pro | 3:5.44-1ubuntu2 | vulnerable |
| Ubuntu | stunnel4 | pro | 3:5.44-1ubuntu3 | vulnerable |
| Ubuntu | stunnel4 | pro | 3:5.44-1ubuntu3+esm1 | fixed |
| Ubuntu | stunnel4 | 20.04 | 3:5.55-2build1 | vulnerable |
| Ubuntu | stunnel4 | 20.04 | 3:5.56-1 | vulnerable |
| Ubuntu | stunnel4 | 20.04 | 3:5.56-1ubuntu0.2 | fixed |
| Suse | stunnel | linux enterprise high performance computing 15-espos | 5.44-3.8.1 | fixed |
| Suse | stunnel | linux enterprise high performance computing 15-ltss | 5.44-3.8.1 | fixed |
| Suse | stunnel | linux enterprise high performance computing 15 sp1-espos | 5.44-3.8.1 | fixed |
| Suse | stunnel | linux enterprise high performance computing 15 sp1-ltss | 5.44-3.8.1 | fixed |
| Suse | stunnel | linux enterprise server 15-ltss | 5.44-3.8.1 | fixed |
| Suse | stunnel | linux enterprise server 15 sp1-bcl | 5.44-3.8.1 | fixed |
| Suse | stunnel | linux enterprise server 15 sp1-ltss | 5.44-3.8.1 | fixed |
| Suse | stunnel | linux enterprise server for sap applications 15 | 5.44-3.8.1 | fixed |
| Suse | stunnel | linux enterprise server for sap applications 15 sp1 | 5.44-3.8.1 | fixed |
| Suse | stunnel | manager proxy 4.0 | 5.44-3.8.1 | fixed |
| Suse | stunnel | manager retail branch server 4.0 | 5.44-3.8.1 | fixed |
| Suse | stunnel | manager server 4.0 | 5.44-3.8.1 | fixed |
| Suse | stunnel | enterprise storage 6 | 5.44-3.8.1 | fixed |
| Ubuntu | stunnel4 | pro | 3:5.39-2 | vulnerable |
| Ubuntu | stunnel4 | pro | 3:5.42-1 | vulnerable |
| Ubuntu | stunnel4 | pro | 3:5.44-1ubuntu1 | vulnerable |
| Ubuntu | stunnel4 | pro | 3:5.44-1ubuntu2 | vulnerable |
| Ubuntu | stunnel4 | pro | 3:5.44-1ubuntu3 | vulnerable |
| Ubuntu | stunnel4 | pro | 3:5.44-1ubuntu3+esm1 | fixed |
| Ubuntu | stunnel4 | 20.04 | 3:5.55-2build1 | vulnerable |
| Ubuntu | stunnel4 | 20.04 | 3:5.56-1 | vulnerable |
| Ubuntu | stunnel4 | 20.04 | 3:5.56-1ubuntu0.2 | fixed |
| Opensuse | stunnel | leap 15.2 | 5.57-lp152.2.6.1 | fixed |
| Suse | stunnel | linux enterprise module for server applications 15 sp2 | 5.57-3.11.1 | fixed |
Fixed-version evidence
| Distribution | Package | Type | Release | Fixed version | Urgency | Origin | Bugs |
|---|---|---|---|---|---|---|---|
| Debian | stunnel4 | source | trixie | 3:5.56+dfsg-8 | not yet assigned | Not reported | [982578] |
| Debian | stunnel4 | source | bookworm | 3:5.56+dfsg-8 | not yet assigned | Not reported | [982578] |
| Ubuntu | stunnel4 | deb | pro | 3:5.44-1ubuntu3+esm1 | Not reported | USN-6901-1 | Not reported |
| Ubuntu | stunnel4 | deb | 20.04 | 3:5.56-1ubuntu0.2 | Not reported | USN-6901-1 | Not reported |
| Suse | stunnel | rpm | linux enterprise high performance computing 15-espos | 5.44-3.8.1 | Not reported | SUSE-SU-2021:1465-1 | Not reported |
| Suse | stunnel | rpm | linux enterprise high performance computing 15-ltss | 5.44-3.8.1 | Not reported | SUSE-SU-2021:1465-1 | Not reported |
| Suse | stunnel | rpm | linux enterprise high performance computing 15 sp1-espos | 5.44-3.8.1 | Not reported | SUSE-SU-2021:1465-1 | Not reported |
| Suse | stunnel | rpm | linux enterprise high performance computing 15 sp1-ltss | 5.44-3.8.1 | Not reported | SUSE-SU-2021:1465-1 | Not reported |
| Suse | stunnel | rpm | linux enterprise server 15-ltss | 5.44-3.8.1 | Not reported | SUSE-SU-2021:1465-1 | Not reported |
| Suse | stunnel | rpm | linux enterprise server 15 sp1-bcl | 5.44-3.8.1 | Not reported | SUSE-SU-2021:1465-1 | Not reported |
| Suse | stunnel | rpm | linux enterprise server 15 sp1-ltss | 5.44-3.8.1 | Not reported | SUSE-SU-2021:1465-1 | Not reported |
| Suse | stunnel | rpm | linux enterprise server for sap applications 15 | 5.44-3.8.1 | Not reported | SUSE-SU-2021:1465-1 | Not reported |
| Suse | stunnel | rpm | linux enterprise server for sap applications 15 sp1 | 5.44-3.8.1 | Not reported | SUSE-SU-2021:1465-1 | Not reported |
| Suse | stunnel | rpm | manager proxy 4.0 | 5.44-3.8.1 | Not reported | SUSE-SU-2021:1465-1 | Not reported |
| Suse | stunnel | rpm | manager retail branch server 4.0 | 5.44-3.8.1 | Not reported | SUSE-SU-2021:1465-1 | Not reported |
| Suse | stunnel | rpm | manager server 4.0 | 5.44-3.8.1 | Not reported | SUSE-SU-2021:1465-1 | Not reported |
| Suse | stunnel | rpm | enterprise storage 6 | 5.44-3.8.1 | Not reported | SUSE-SU-2021:1465-1 | Not reported |
| Ubuntu | stunnel4 | deb | pro | 3:5.44-1ubuntu3+esm1 | Not reported | UBUNTU-CVE-2021-20230 | Not reported |
| Ubuntu | stunnel4 | deb | 20.04 | 3:5.56-1ubuntu0.2 | Not reported | UBUNTU-CVE-2021-20230 | Not reported |
| Opensuse | stunnel | rpm | leap 15.2 | 5.57-lp152.2.6.1 | Not reported | OPENSUSE-SU-2021:0409-1 | Not reported |
| Suse | stunnel | rpm | linux enterprise module for server applications 15 sp2 | 5.57-3.11.1 | Not reported | SUSE-SU-2021:0772-1 | Not reported |
OpenFactory catalog packages
[Debian 12 (Bookworm)]
- [stunnel4]Fixed
Details (2)
3:5.68-2+deb12u1· amd64 · bookwormFixed · Fixed:
3:5.56+dfsg-8dsa · stunnel4 · debian · bookworm; dsa · stunnel4 · debian · 12
3:5.68-2+deb12u1· arm64 · bookwormFixed · Fixed:
3:5.56+dfsg-8dsa · stunnel4 · debian · bookworm; dsa · stunnel4 · debian · 12
[Debian 13 (Trixie)]
- [stunnel4]Fixed
Details (2)
3:5.74-2· amd64 · trixieFixed · Fixed:
3:5.56+dfsg-8dsa · stunnel4 · debian · 13
3:5.74-2· arm64 · trixieFixed · Fixed:
3:5.56+dfsg-8dsa · stunnel4 · debian · 13
Observed:
References
- [https://access.redhat.com/errata/RHSA-2021:0618]
- [https://ftp.suse.com/pub/projects/security/csaf/rhsa-2021_0618.json]
- [https://osv.dev/vulnerability/DEBIAN-CVE-2021-20230]
- [https://osv.dev/vulnerability/SUSE-SU-2021:0772-1]
- [https://osv.dev/vulnerability/SUSE-SU-2021:1465-1]
- [https://osv.dev/vulnerability/UBUNTU-CVE-2021-20230]
- [https://osv.dev/vulnerability/USN-6901-1]
- [https://osv.dev/vulnerability/openSUSE-SU-2021:0409-1]
- [https://security-tracker.debian.org/tracker/CVE-2021-20230]
- [https://wid.cert-bund.de/.well-known/csaf/white/2021/wid-sec-w-2024-1674.json]
[CERT-Bund public advisories] · [Debian Security Tracker] · [FIRST EPSS] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX] · [SUSE security advisories and VEX]