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.

The remote Alibaba Cloud Linux 3 host has packages installed that are affected by a vulnerability as referenced in the ALINUX3-SA-2021:0011 advisory.

    Package updates are available for Alibaba Cloud Linux 3 that fix the following vulnerabilities:

    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. 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.

Tenable has extracted the preceding description block directly from the Alibaba Cloud Linux security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote Ubuntu 18.04 LTS / 20.04 LTS host has a package installed that is affected by a vulnerability as referenced in the USN-6901-1 advisory.

    It was discovered that stunnel did not properly validate client certificates when configured to use both     the redirect and verifyChain options. A remote attacker could potentially use this issue to obtain     sensitive information by accessing the tunneled service.

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote Rocky Linux 8 host has packages installed that are affected by a vulnerability as referenced in the RLSA-2021:0618 advisory.

  - 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. (CVE-2021-20230)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote AlmaLinux 8 host has a package installed that is affected by a vulnerability as referenced in the ALSA-2021:0618 advisory.

  - 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. (CVE-2021-20230)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote NewStart CGSL host, running version MAIN 6.02, has stunnel packages installed that are affected by a vulnerability:

  - 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. (CVE-2021-20230)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote host is affected by the vulnerability described in GLSA-202105-02 (stunnel: Improper certificate validation)

    It was discovered that stunnel did not correctly verified the client       certificate when options &ldquo;redirect&rdquo; and &ldquo;verifyChain&rdquo; are used.
  Impact :

    A remote attacker could send a specially crafted certificate, possibly       resulting in a breach of integrity or confidentiality.
  Workaround :

    There is no known workaround at this time.

According to the version of the stunnel package installed, the EulerOS installation on the remote host is affected by the following vulnerability :

  - 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.(CVE-2021-20230)

Note that Tenable Network Security has extracted the preceding description block directly from the EulerOS security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

The remote Redhat Enterprise Linux 8 host has a package installed that is affected by a vulnerability as referenced in the RHSA-2021:0619 advisory.

    Stunnel is a wrapper for network connections. It can be used to tunnel an unencrypted network connection     over an encrypted connection (encrypted using SSL or TLS) or to provide an encrypted means of connecting     to services that do not natively support encryption.

    Security Fix(es):

    * stunnel: client certificate not correctly verified when redirect and verifyChain options are used     (CVE-2021-20230)

    For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and     other related information, refer to the CVE page(s) listed in the References section.

Tenable has extracted the preceding description block directly from the Red Hat Enterprise Linux security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote Redhat Enterprise Linux 8 host has a package installed that is affected by a vulnerability as referenced in the RHSA-2021:0620 advisory.

    Stunnel is a wrapper for network connections. It can be used to tunnel an unencrypted network connection     over an encrypted connection (encrypted using SSL or TLS) or to provide an encrypted means of connecting     to services that do not natively support encryption.

    Security Fix(es):

    * stunnel: client certificate not correctly verified when redirect and verifyChain options are used     (CVE-2021-20230)

    For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and     other related information, refer to the CVE page(s) listed in the References section.

Tenable has extracted the preceding description block directly from the Red Hat Enterprise Linux security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote Redhat Enterprise Linux 8 host has a package installed that is affected by a vulnerability as referenced in the RHSA-2021:0618 advisory.

    Stunnel is a wrapper for network connections. It can be used to tunnel an unencrypted network connection     over an encrypted connection (encrypted using SSL or TLS) or to provide an encrypted means of connecting     to services that do not natively support encryption.

    Security Fix(es):

    * stunnel: client certificate not correctly verified when redirect and verifyChain options are used     (CVE-2021-20230)

    For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and     other related information, refer to the CVE page(s) listed in the References section.

Tenable has extracted the preceding description block directly from the Red Hat Enterprise Linux security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

This update for stunnel fixes the following issues :

Security fix: [bsc#1177580, bsc#1182529, CVE-2021-20230]

  - 'redirect' option does not properly handle 'verifyChain     = yes'

Note that Tenable Network Security has extracted the preceding description block directly from the SUSE security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

The remote Oracle Linux 8 host has a package installed that is affected by a vulnerability as referenced in the ELSA-2021-0618 advisory.

    [5.56-5]
    - Fix CVE-2021-20230 stunnel: client certificate not       correctly verified when redirect and verifyChain options are used.

Tenable has extracted the preceding description block directly from the Oracle Linux security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

This update for stunnel fixes the following issues :

  - Security fix: [bsc#1177580, bsc#1182529, CVE-2021-20230]

  - 'redirect' option does not properly handle 'verifyChain     = yes'

This update was imported from the SUSE:SLE-15-SP2:Update update project.

The remote CentOS Linux 8 host has a package installed that is affected by a vulnerability as referenced in the CESA-2021:0618 advisory.

  - stunnel: client certificate not correctly verified when redirect and verifyChain options are used     (CVE-2021-20230)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Severity
236598	Alibaba Cloud Linux 3 : 0011: stunnel (ALINUX3-SA-2021:0011)	Nessus	Alibaba Cloud Linux Local Security Checks	high
202590	Ubuntu 18.04 LTS / 20.04 LTS : stunnel vulnerability (USN-6901-1)	Nessus	Ubuntu Local Security Checks	high
184711	Rocky Linux 8 : stunnel (RLSA-2021:0618)	Nessus	Rocky Linux Local Security Checks	high
157658	AlmaLinux 8 : stunnel (ALSA-2021:0618)	Nessus	Alma Linux Local Security Checks	high
154510	NewStart CGSL MAIN 6.02 : stunnel Vulnerability (NS-SA-2021-0123)	Nessus	NewStart CGSL Local Security Checks	high
150016	GLSA-202105-02 : stunnel: Improper certificate validation	Nessus	Gentoo Local Security Checks	high
149591	EulerOS 2.0 SP8 : stunnel (EulerOS-SA-2021-1889)	Nessus	Huawei Local Security Checks	high
149507	RHEL 8 : stunnel (RHSA-2021:0619)	Nessus	Red Hat Local Security Checks	high
149506	RHEL 8 : stunnel (RHSA-2021:0620)	Nessus	Red Hat Local Security Checks	high
149504	RHEL 8 : stunnel (RHSA-2021:0618)	Nessus	Red Hat Local Security Checks	high
149248	SUSE SLES15 Security Update : stunnel (SUSE-SU-2021:1465-1)	Nessus	SuSE Local Security Checks	high
148551	Oracle Linux 8 : stunnel (ELSA-2021-0618)	Nessus	Oracle Linux Local Security Checks	high
147781	SUSE SLES15 Security Update : stunnel (SUSE-SU-2021:0772-1)	Nessus	SuSE Local Security Checks	high
147776	openSUSE Security Update : stunnel (openSUSE-2021-409)	Nessus	SuSE Local Security Checks	high
146871	CentOS 8 : stunnel (CESA-2021:0618)	Nessus	CentOS Local Security Checks	high

Detections

Analytics

CVE-2021-20230

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Tenable Plugins

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