Mozilla Firefox prior to 3.6 has a DoS vulnerability due to an issue in the validation of certificates.

dirmngr: Improper dealing with blocking system calls, when verifying a certificate

dirmngr before 2.1.0 improperly handles certain system calls, which allows remote attackers to cause a denial of service (DOS) via a specially-crafted certificate.

offlineimap before 6.3.4 added support for SSL server certificate validation but it is still possible to use SSL v2 protocol, which is a flawed protocol with multiple security deficiencies.

offlineimap before 6.3.2 does not check for SSL server certificate validation when "ssl = yes" option is specified which can allow man-in-the-middle attacks.

Mercurial: Doesn't verify subject Common Name

Mercurial before 1.6.4 fails to verify the Common Name field of SSL certificates which allows remote attackers who acquire a certificate signed by a Certificate Authority to perform a man-in-the-middle attack.

The jruby-openssl gem before 0.6 for JRuby mishandles SSL certificate validation.

GUI: Man in the middle attack possible on the GUI to Backend SSL connection

In RHEV-M VDC 2.2.0, it was found that the SSL certificate was not verified when using the client-side Red Hat Enterprise Virtualization Manager interface (a Windows Presentation Foundation (WPF) XAML browser application) to connect to the Red Hat Enterprise Virtualization Manager. An attacker on the local network could use this flaw to conduct a man-in-the-middle attack, tricking the user into thinking they are viewing the Red Hat Enterprise Virtualization Manager when the content is actually attacker-controlled, or modifying actions a user requested Red Hat Enterprise Virtualization Manager to perform.

A flaw in Mozilla's embedded certificate code might allow web sites to install root certificates on devices without user approval.

(WPA-Enterprise): Verify that the certificate is from trusted CA and matches the specified subject

NetworkManager 0.9.x does not pin a certificate's subject to an ESSID when 802.11X authentication is used.

qBittorrent: RCE Vulnerability in qBittorrent Due to Improper SSL/TLS Certificate Validation

qBittorrent before 5.0.1 proceeds with use of https URLs even after certificate validation errors.

QBiC CLOUD CC-2L v1.1.30 and earlier and Safie One v1.8.2 and earlier do not properly validate certificates, which may allow a network-adjacent unauthenticated attacker to obtain and/or alter communications of the affected product via a man-in-the-middle attack.

IBM Concert improper certificate validation

IBM Concert 1.0.0 and 1.0.1 vulnerable to attacks that rely on the use of cookies without the SameSite attribute.

Insecure Trust of certificates using collision hash functions in Bitdefender Total Security HTTPS Scanning (VA-11239)

A vulnerability has been identified in the Bitdefender Total Security HTTPS scanning functionality where the product incorrectly checks the site's certificate, which allows an attacker to make MITM SSL connections to an arbitrary site. The product trusts certificates that are issued using the MD5 and SHA1 collision hash functions which allow attackers to create rogue certificates that appear legitimate.

Improper Certificate Validation in Bitdefender Total Security HTTPS Scanning (VA-11158)

A vulnerability has been identified in Bitdefender Total Security HTTPS scanning functionality where the software fails to properly validate website certificates. Specifically, if a site certificate lacks the "Server Authentication" specification in the Extended Key Usage extension, the product does not verify the certificate's compliance with the site, deeming such certificates as valid. This flaw could allow an attacker to perform a Man-in-the-Middle (MITM) attack, intercepting and potentially altering communications between the user and the website.

Insecure Trust of Self-Signed Certificates in Bitdefender Total Security HTTPS Scanning (VA-11164)

A vulnerability has been discovered in Bitdefender Total Security HTTPS scanning functionality that results in the improper trust of self-signed certificates. The product is found to trust certificates signed with the RIPEMD-160 hashing algorithm without proper validation, allowing an attacker to establish MITM SSL connections to arbitrary sites.

Insecure Trust of Basic Constraints certificate in Bitdefender Total Security HTTPS Scanning (VA-11210)

A vulnerability has been identified in Bitdefender Total Security HTTPS scanning functionality where the software trusts a certificate issued by an entity that isn't authorized to issue certificates. This occurs when the "Basic Constraints" extension in the certificate indicates that it is meant to be an "End Entity”. This flaw could allow an attacker to perform a Man-in-the-Middle (MITM) attack, intercepting and potentially altering communications between the user and the website.

HTTPS Certificate Validation Issue in Bitdefender Safepay (VA-11167)

A vulnerability has been identified in Bitdefender Safepay's handling of HTTPS connections. The issue arises when the product blocks a connection due to an untrusted server certificate but allows the user to add the site to exceptions, resulting in the product trusting the certificate for subsequent HTTPS scans. This vulnerability allows an attacker to perform a Man-in-the-Middle (MITM) attack by using a self-signed certificate, which the product will trust after the site has been added to exceptions. This can lead to the interception and potential alteration of secure communications.

Cisco Nexus Dashboard Orchestrator SSL Certificate Validation Vulnerability

A vulnerability in the SSL/TLS implementation of Cisco Nexus Dashboard Orchestrator (NDO) could allow an unauthenticated, remote attacker to intercept sensitive information from an affected device.  This vulnerability exists because the Cisco NDO Validate Peer Certificate site management feature validates the certificates for Cisco Application Policy Infrastructure Controller (APIC), Cisco Cloud Network Controller (CNC), and Cisco Nexus Dashboard only when a new site is added or an existing one is reregistered. An attacker could exploit this vulnerability by using machine-in-the-middle techniques to intercept the traffic between the affected device and Cisco NDO and then using a crafted certificate to impersonate the affected device. A successful exploit could allow the attacker to learn sensitive information during communications between these devices.

IBM Storage Defender improper certificate validation

IBM Storage Defender 2.0.0 through 2.0.7 on-prem defender-sensor-cmd CLI does not validate server name during registration and unregistration operations which could expose sensitive information to an attacker with access to the system.

An improper certificate validation vulnerability [CWE-295] in FortiClientWindows 6.4 all versions, 7.0.0 through 7.0.7, FortiClientMac 6.4 all versions, 7.0 all versions, 7.2.0 through 7.2.4, FortiClientLinux 6.4 all versions, 7.0 all versions, 7.2.0 through 7.2.4, FortiClientAndroid 6.4 all versions, 7.0 all versions, 7.2.0 and FortiClientiOS 5.6 all versions, 6.0.0 through 6.0.1, 7.0.0 through 7.0.6 SAML SSO feature may allow an unauthenticated attacker to man-in-the-middle the communication between the FortiClient and  both the service provider and the identity provider.