Test ID:	1.3.6.1.4.1.25623.1.0.145406
Category:	Denial of Service
Title:	OpenSSL: Incorrect SSLv2 rollback protection (CVE-2021-23839) - Windows
Summary:	OpenSSL is prone to an incorrect SSLv2 rollback protection vulnerability.
Description:	Summary: OpenSSL is prone to an incorrect SSLv2 rollback protection vulnerability. Vulnerability Insight: OpenSSL 1.0.2 supports SSLv2. If a client attempts to negotiate SSLv2 with a server that is configured to support both SSLv2 and more recent SSL and TLS versions then a check is made for a version rollback attack when unpadding an RSA signature. Clients that support SSL or TLS versions greater than SSLv2 are supposed to use a special form of padding. A server that supports greater than SSLv2 is supposed to reject connection attempts from a client where this special form of padding is present, because this indicates that a version rollback has occurred (i.e. both client and server support greater than SSLv2, and yet this is the version that is being requested). The implementation of this padding check inverted the logic so that the connection attempt is accepted if the padding is present, and rejected if it is absent. This means that such as server will accept a connection if a version rollback attack has occurred. Further the server will erroneously reject a connection if a normal SSLv2 connection attempt is made. Affected Software/OS: OpenSSL versions 1.0.2s - 1.0.2x. Solution: Update to version 1.0.2y, 1.1.1j or later. See the references for more details. CVSS Score: 4.3 CVSS Vector: AV:N/AC:M/Au:N/C:N/I:P/A:N
Cross-Ref:	Common Vulnerability Exposure (CVE) ID: CVE-2021-23839 https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff;h=30919ab80a478f2d81f2e9acdcca3fa4740cd547 https://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA44846 https://security.netapp.com/advisory/ntap-20210219-0009/ https://www.openssl.org/news/secadv/20210216.txt https://www.oracle.com//security-alerts/cpujul2021.html https://www.oracle.com/security-alerts/cpuApr2021.html https://www.oracle.com/security-alerts/cpuapr2022.html https://www.oracle.com/security-alerts/cpuoct2021.html
Copyright	Copyright (C) 2021 Greenbone Networks GmbH

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