The X509_V_FLAG_X509_STRICT flag enables additional security checks of the certificates present in a certificate chain. It is not set by default. Starting from OpenSSL version 1.1.1h a check to disallow certificates in the chain that have explicitly encoded elliptic curve parameters was added as an additional strict check. An error in the implementation of this check meant that the result of a previous check to confirm that certificates in the chain are valid CA certificates was overwritten. This effectively bypasses the check that non-CA certificates must not be able to issue other certificates. If a "purpose" has been configured then there is a subsequent opportunity for checks that the certificate is a valid CA. All of the named "purpose" values implemented in libcrypto perform this check. Therefore, where a purpose is set the certificate chain will still be rejected even when the strict flag has been used. A purpose is set by default in libssl client and server certificate verification routines, but it can be overridden or removed by an application. In order to be affected, an application must explicitly set the X509_V_FLAG_X509_STRICT verification flag and either not set a purpose for the certificate verification or, in the case of TLS client or server applications, override the default purpose. OpenSSL versions 1.1.1h and newer are affected by this issue. Users of these versions should upgrade to OpenSSL 1.1.1k. OpenSSL 1.0.2 is not impacted by this issue. Fixed in OpenSSL 1.1.1k (Affected 1.1.1h-1.1.1j).

Burp Suite Community Edition 1.7.32 and 1.7.33 fail to validate the server certificate in a couple of HTTPS requests which allows a man in the middle to modify or view traffic.

An open redirect vulnerability in LabKey Server Community Edition before 18.3.0-61806.763 via the /__r1/ returnURL parameter allows an unauthenticated remote attacker to redirect users to arbitrary web sites.

An Improper Certificate Validation vulnerability exists in Tenable Security Center where an authenticated, privileged attacker could intercept email messages sent from Security Center via a rogue SMTP server.

Nessus AMI versions 8.12.0 and earlier were found to either not validate, or incorrectly validate, a certificate which could allow an attacker to spoof a trusted entity by using a man-in-the-middle (MITM) attack.

The Certificate Trust Policy component in Apple Mac OS X before 10.6.8 does not perform CRL checking for Extended Validation (EV) certificates that lack OCSP URLs, which might allow man-in-the-middle attackers to spoof an SSL server via a revoked certificate.

lib/oauth/consumer.rb in the oauth-ruby gem through 0.5.4 for Ruby does not verify server X.509 certificates if a certificate bundle cannot be found, which allows man-in-the-middle attackers to spoof servers and obtain sensitive information.

Jenkins Mailer Plugin 1.32 and earlier does not perform hostname validation when connecting to the configured SMTP server.

Jenkins Email Extension Plugin 2.75 and earlier does not perform hostname validation when connecting to the configured SMTP server.

Incorrect validation of the TLS SNI hostname in osquery versions after 2.9.0 and before 4.2.0 could allow an attacker to MITM osquery traffic in the absence of a configured root chain of trust.

Improper Certificate Validation in GitHub repository pyload/pyload prior to 0.5.0b3.dev44.

In faye-websocket before version 0.11.0, there is a lack of certification validation in TLS handshakes. The `Faye::WebSocket::Client` class uses the `EM::Connection#start_tls` method in EventMachine to implement the TLS handshake whenever a `wss:` URL is used for the connection. This method does not implement certificate verification by default, meaning that it does not check that the server presents a valid and trusted TLS certificate for the expected hostname. That means that any `wss:` connection made using this library is vulnerable to a man-in-the-middle attack, since it does not confirm the identity of the server it is connected to. For further background information on this issue, please see the referenced GitHub Advisory. Upgrading `faye-websocket` to v0.11.0 is recommended.

Missing validation of server certificates for out-going connections in Nextcloud Social < 0.4.0 allowed a man-in-the-middle attack.

The komoot GmbH "Komoot - Cycling & Hiking Maps" app before 9.3.2 -- aka komoot-cycling-hiking-maps/id447374873 -- for iOS does not verify X.509 certificates from SSL servers, which allows man-in-the-middle attackers to spoof servers and obtain sensitive information via a crafted certificate.

Android App 'MyPallete' and some of the Android banking applications based on 'MyPallete' do not verify X.509 certificates from servers, and also do not properly validate certificates with host-mismatch, which allows man-in-the-middle attackers to spoof servers and obtain sensitive information via a crafted certificate.

A flaw was found in all Openshift Enterprise versions using the openshift elasticsearch plugin. An attacker with knowledge of the given name used to authenticate and access Elasticsearch can later access it without the token, bypassing authentication. This attack also requires that the Elasticsearch be configured with an external route, and the data accessed is limited to the indices.

Accepting arbitrary Subject Alternative Name (SAN) types, unless a PKI is specifically defined to use a particular SAN type, can result in bypassing name-constrained intermediates. Node.js < 12.22.9, < 14.18.3, < 16.13.2, and < 17.3.1 was accepting URI SAN types, which PKIs are often not defined to use. Additionally, when a protocol allows URI SANs, Node.js did not match the URI correctly.Versions of Node.js with the fix for this disable the URI SAN type when checking a certificate against a hostname. This behavior can be reverted through the --security-revert command-line option.

Apache Sling Commons Messaging Mail provides a simple layer on top of JavaMail/Jakarta Mail for OSGi to send mails via SMTPS. To reduce the risk of "man in the middle" attacks additional server identity checks must be performed when accessing mail servers. For compatibility reasons these additional checks are disabled by default in JavaMail/Jakarta Mail. The SimpleMailService in Apache Sling Commons Messaging Mail 1.0 lacks an option to enable these checks for the shared mail session. A user could enable these checks nevertheless by accessing the session via the message created by SimpleMessageBuilder and setting the property mail.smtps.ssl.checkserveridentity to true. Apache Sling Commons Messaging Mail 2.0 adds support for enabling server identity checks and these checks are enabled by default. - https://javaee.github.io/javamail/docs/SSLNOTES.txt - https://javaee.github.io/javamail/docs/api/com/sun/mail/smtp/package-summary.html - https://github.com/eclipse-ee4j/mail/issues/429

e2guardian v5.4.x <= v5.4.3r is affected by missing SSL certificate validation in the SSL MITM engine. In standalone mode (i.e., acting as a proxy or a transparent proxy), with SSL MITM enabled, e2guardian, if built with OpenSSL v1.1.x, did not validate hostnames in certificates of the web servers that it connected to, and thus was itself vulnerable to MITM attacks.

niconico App for iOS before 6.38 does not verify SSL certificates which could allow remote attackers to execute man-in-the-middle attacks.

The Thycotic Password Manager Secret Server application through 2.3 for iOS does not verify X.509 certificates from SSL servers, which allows man-in-the-middle attackers to spoof servers and obtain sensitive information via a crafted certificate.

Rakuten card App for iOS 5.2.0 through 5.2.4 does not verify SSL certificates which might allow remote attackers to execute man-in-the-middle attacks.

OpenVPN 3 Core Library version 3.6 and 3.6.1 allows a man-in-the-middle attacker to bypass the certificate authentication by issuing an unrelated server certificate using the same hostname found in the verify-x509-name option in a client configuration.

The AWV component of Mitel MiCollab before 9.3 could allow an attacker to perform a Man-In-the-Middle attack due to improper TLS negotiation. A successful exploit could allow an attacker to view and modify data.

Codehaus XFire 1.2.6 and earlier, as used in the Amazon EC2 API Tools Java library and other products, does not verify that the server hostname matches a domain name in the subject's Common Name (CN) or subjectAltName field of the X.509 certificate, which allows man-in-the-middle attackers to spoof SSL servers via an arbitrary valid certificate.

em-imap 0.5 uses the library eventmachine in an insecure way that allows an attacker to perform a man-in-the-middle attack against users of the library. The hostname in a TLS server certificate is not verified.

core/imap/MCIMAPSession.cpp in Canary Mail before 3.22 has Missing SSL Certificate Validation for IMAP in STARTTLS mode.

EM-HTTP-Request 1.1.5 uses the library eventmachine in an insecure way that allows an attacker to perform a man-in-the-middle attack against users of the library. The hostname in a TLS server certificate is not verified.

The SSLVerifySignedServerKeyExchange function in libsecurity_ssl/lib/sslKeyExchange.c in the Secure Transport feature in the Data Security component in Apple iOS 6.x before 6.1.6 and 7.x before 7.0.6, Apple TV 6.x before 6.0.2, and Apple OS X 10.9.x before 10.9.2 does not check the signature in a TLS Server Key Exchange message, which allows man-in-the-middle attackers to spoof SSL servers by (1) using an arbitrary private key for the signing step or (2) omitting the signing step.

The SNKRDUNK Market Place App for iOS versions prior to 2.2.0 does not verify server certificate properly, which allows man-in-the-middle attackers to eavesdrop on and/or alter encrypted communication via a crafted certificate.

The int_x509_param_set_hosts function in lib/libcrypto/x509/x509_vpm.c in LibreSSL 2.7.0 before 2.7.1 does not support a certain special case of a zero name length, which causes silent omission of hostname verification, and consequently allows man-in-the-middle attackers to spoof servers and obtain sensitive information via a crafted certificate. NOTE: the LibreSSL documentation indicates that this special case is supported, but the BoringSSL documentation does not.

When using an OCSP responder Apache Tomcat Native 1.2.0 to 1.2.16 and 1.1.23 to 1.1.34 did not correctly handle invalid responses. This allowed for revoked client certificates to be incorrectly identified. It was therefore possible for users to authenticate with revoked certificates when using mutual TLS. Users not using OCSP checks are not affected by this vulnerability.

WebHybridClient.java in PayPal 5.3 and earlier for Android ignores SSL errors, which allows man-in-the-middle attackers to spoof servers and obtain sensitive information.

A vulnerability has been identified in Siveillance VMS Video for Android (All versions < V12.1a (2018 R1)), Siveillance VMS Video for iOS (All versions < V12.1a (2018 R1)). Improper certificate validation could allow an attacker in a privileged network position to read data from and write data to the encrypted communication channel between the app and a server. The security vulnerability could be exploited by an attacker in a privileged network position which allows intercepting the communication channel between the affected app and a server (such as Man-in-the-Middle). Furthermore, an attacker must be able to generate a certificate that results for the validation algorithm in a checksum identical to a trusted certificate. Successful exploitation requires no user interaction. The vulnerability could allow reading data from and writing data to the encrypted communication channel between the app and a server, impacting the communication's confidentiality and integrity. At the time of advisory publication no public exploitation of this security vulnerability was known. Siemens confirms the security vulnerability and provides mitigations to resolve the security issue.

ELECOM WRC-300FEBK-S contains an improper certificate validation vulnerability. Via a man-in-the-middle attack, an attacker may alter the communication response. As a result, an arbitrary OS command may be executed on the affected device.

The ServerTrustManager component in the Ignite Realtime Smack XMPP API before 4.0.0-rc1 does not verify basicConstraints and nameConstraints in X.509 certificate chains from SSL servers, which allows man-in-the-middle attackers to spoof servers and obtain sensitive information via a crafted certificate chain.

A vulnerability in the Cisco Identity Services Engine (ISE) integration feature of the Cisco DNA Center Software could allow an unauthenticated, remote attacker to gain unauthorized access to sensitive data. The vulnerability is due to an incomplete validation of the X.509 certificate used when establishing a connection between DNA Center and an ISE server. An attacker could exploit this vulnerability by supplying a crafted certificate and could then intercept communications between the ISE and DNA Center. A successful exploit could allow the attacker to view and alter sensitive information that the ISE maintains about clients that are connected to the network.

A vulnerability in the Cisco Advanced Malware Protection (AMP) for Endpoints integration of Cisco AsyncOS for Cisco Email Security Appliance (ESA) and Cisco Web Security Appliance (WSA) could allow an unauthenticated, remote attacker to intercept traffic between an affected device and the AMP servers. This vulnerability is due to improper certificate validation when an affected device establishes TLS connections. A man-in-the-middle attacker could exploit this vulnerability by sending a crafted TLS packet to an affected device. A successful exploit could allow the attacker to spoof a trusted host and then extract sensitive information or alter certain API requests.

Multiple vulnerabilities in Cisco Data Center Network Manager (DCNM) could allow an attacker to spoof a trusted host or construct a man-in-the-middle attack to extract sensitive information or alter certain API requests. These vulnerabilities are due to insufficient certificate validation when establishing HTTPS requests with the affected device. For more information about these vulnerabilities, see the Details section of this advisory.

IBM QRadar SIEM 7.2.8 and 7.3 does not validate, or incorrectly validates, a certificate. This weakness might allow an attacker to spoof a trusted entity by using a man-in-the-middle (MITM) attack. IBM X-force ID: 133120.

TLS session reuse can lead to host certificate verification bypass in node version < 12.18.0 and < 14.4.0.

The contribution feature in Zamboni does not verify that the server hostname matches a domain name in the subject's Common Name (CN) or subjectAltName field of the X.509 certificate, which allows man-in-the-middle attackers to spoof SSL servers via an arbitrary valid certificate, related to use of the Python urllib2 library.

The Chase mobile banking application for Android does not verify that the server hostname matches a domain name in the subject's Common Name (CN) or subjectAltName field of the X.509 certificate, which allows man-in-the-middle attackers to spoof SSL servers via an arbitrary valid certificate, related to overriding the default X509TrustManager. NOTE: this vulnerability was fixed in the summer of 2012, but the version number was not changed or is not known.

Avast AntiTrack before 1.5.1.172 and AVG Antitrack before 2.0.0.178 proxies traffic to HTTPS sites but does not validate certificates, and thus a man-in-the-middle can host a malicious website using a self-signed certificate. No special action necessary by the victim using AntiTrack with "Allow filtering of HTTPS traffic for tracking detection" enabled. (This is the default configuration.)

Cerulean Studios Trillian 3.1 Basic does not check SSL certificates during MSN authentication, which allows remote attackers to obtain MSN credentials via a man-in-the-middle attack with a spoofed SSL certificate.

FilesAnywhere does not verify that the server hostname matches a domain name in the subject's Common Name (CN) or subjectAltName field of the X.509 certificate, which allows man-in-the-middle attackers to spoof SSL servers via an arbitrary valid certificate.

Apache Commons HttpClient 3.x, as used in Amazon Flexible Payments Service (FPS) merchant Java SDK and other products, does not verify that the server hostname matches a domain name in the subject's Common Name (CN) or subjectAltName field of the X.509 certificate, which allows man-in-the-middle attackers to spoof SSL servers via an arbitrary valid certificate.