13 May 2015
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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2015.1290 MS15-055: Vulnerability in Schannel Could Allow Information Disclosure (3061518) - Important 13 May 2015 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Microsoft Windows Publisher: Microsoft Operating System: Windows Impact/Access: Reduced Security -- Remote/Unauthenticated Resolution: Patch/Upgrade CVE Names: CVE-2015-1716 Original Bulletin: https://technet.microsoft.com/en-us/library/security/MS15-055 - --------------------------BEGIN INCLUDED TEXT-------------------- MS15-055: Vulnerability in Schannel Could Allow Information Disclosure (3061518) - Important Bulletin Number: MS15-055 Bulletin Title: Vulnerability in Schannel Could Allow Information Disclosure Severity: Important KB Article: 3061518 Version: 1.0 Published Date: May 12, 2015 Executive Summary This security update resolves a vulnerability in Microsoft Windows. The vulnerability could allow information disclosure when Secure Channel (Schannel) allows the use of a weak Diffie-Hellman ephemeral (DFE) key length of 512 bits in an encrypted TLS session. Allowing 512-bit DHE keys makes DHE key exchanges weak and vulnerable to various attacks. A server needs to support 512-bit DHE key lengths for an attack to be successful; the minimum allowable DHE key length in default configurations of Windows servers is 1024 bits. This security update is rated Important for all supported releases of Microsoft Windows. For more information, see the Affected Software section. Affected Software Windows Server 2003 Service Pack 2 Windows Server 2003 x64 Edition Service Pack 2 Windows Server 2003 with SP2 for Itanium-based Systems Windows Vista Service Pack 2 Windows Vista x64 Edition Service Pack 2 Windows Server 2008 for 32-bit Systems Service Pack 2 Windows Server 2008 for x64-based Systems Service Pack 2 Windows Server 2008 for Itanium-based Systems Service Pack 2 Windows 7 for 32-bit Systems Service Pack 1 Windows 7 for x64-based Systems Service Pack 1 Windows Server 2008 R2 for x64-based Systems Service Pack 1 Windows Server 2008 R2 for Itanium-based Systems Service Pack 1 Windows 8 for 32-bit Systems Windows 8 for x64-based Systems Windows 8.1 for 32-bit Systems Windows 8.1 for x64-based Systems Windows Server 2012 Windows Server 2012 R2 Windows RT Windows RT 8.1 Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core installation) Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core installation) Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation) Windows Server 2012 (Server Core installation) Windows Server 2012 R2 (Server Core installation) This update is available via Windows Update only. Vulnerability Information Schannel Information Disclosure Vulnerability - CVE-2015-1716 An information disclosure vulnerability exists in Secure Channel (Schannel) when it allows the use of a weak Diffie-Hellman ephemeral (DFE) key length of 512 bits in an encrypted TLS session. Allowing 512-bit DHE keys makes DHE key exchanges weak and vulnerable to various attacks. The security update addresses the vulnerability by increasing the minimum allowable DHE key length to 1024 bits. Microsoft received information about this vulnerability through coordinated vulnerability disclosure. When this security bulletin was issued, Microsoft had not received any information to indicate that this vulnerability had been publicly used to attack customers. - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. 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It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the author's website to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/render.html?cid=1980 =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: firstname.lastname@example.org Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). 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