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computer vulnerability bulletin CVE-2016-2181

OpenSSL: denial of service via DTLS Window

Synthesis of the vulnerability

An attacker can send a DTLS packet with a large sequence number to an application compiled with OpenSSL, in order to trigger a denial of service.
Impacted software: Blue Coat CAS, ProxyAV, ProxySG par Blue Coat, SGOS by Blue Coat, Cisco ASR, Cisco Aironet, Cisco ATA, Cisco AnyConnect Secure Mobility Client, Cisco ACE, ASA, AsyncOS, Cisco Catalyst, Cisco Content SMA, Cisco ESA, IOS by Cisco, IOS XE Cisco, IOS XR Cisco, Cisco IPS, Nexus by Cisco, NX-OS, Cisco Prime Access Registrar, Prime Collaboration Assurance, Cisco Prime DCNM, Prime Infrastructure, Cisco Prime LMS, Cisco Router, Secure ACS, Cisco CUCM, Cisco Manager Attendant Console, Cisco Unified CCX, Cisco IP Phone, Cisco MeetingPlace, Cisco Wireless IP Phone, Cisco WSA, Cisco Wireless Controller, Debian, BIG-IP Hardware, TMOS, Fedora, FileZilla Server, FortiAnalyzer, FortiAnalyzer Virtual Appliance, FortiGate, FortiGate Virtual Appliance, FortiOS, FreeBSD, FreeRADIUS, hMailServer, AIX, QRadar SIEM, Tivoli Storage Manager, Tivoli Workload Scheduler, Juniper J-Series, Junos OS, Junos Space, NSM Central Manager, NSMXpress, McAfee Email Gateway, NetScreen Firewall, ScreenOS, Nodejs Core, OpenSSL, openSUSE, openSUSE Leap, Oracle Communications, Oracle Directory Server, Oracle Directory Services Plus, Oracle Fusion Middleware, Oracle GlassFish Server, Oracle Identity Management, Oracle iPlanet Web Server, Solaris, Tuxedo, WebLogic, Oracle Web Tier, pfSense, RHEL, SAS Add-in for Microsoft Office, SAS Analytics Pro, Base SAS Software, SAS Enterprise BI Server, SAS Enterprise Guide, SAS Management Console, SAS OLAP Server, SAS SAS/ACCESS, SAS SAS/AF, SAS SAS/CONNECT, SAS SAS/EIS, SAS SAS/ETS, SAS SAS/FSP, SAS SAS/GRAPH, SAS SAS/IML, SAS SAS/OR, SAS SAS/STAT, SAS SAS/Web Report Studio, Slackware, Splunk Enterprise, stunnel, SUSE Linux Enterprise Desktop, SLES, Synology DS***, Synology RS***, Nessus, Ubuntu, WinSCP.
Severity of this computer vulnerability: 2/4.
Consequences of a hack: denial of service on server, denial of service on service, denial of service on client.
Attacker's origin: internet client.
Creation date: 24/08/2016.
Références of this announce: 1996096, 1999395, 1999474, 1999478, 1999479, 1999488, 1999532, 2000095, 2003480, 2003620, 2003673, bulletinapr2017, bulletinjul2016, CERTFR-2016-AVI-333, cisco-sa-20160927-openssl, cpuapr2017, cpujan2018, cpuoct2017, CVE-2016-2181, DLA-637-1, DSA-3673-1, DSA-3673-2, FEDORA-2016-97454404fe, FEDORA-2016-a555159613, FG-IR-16-047, FG-IR-16-048, FG-IR-17-127, FreeBSD-SA-16:26.openssl, JSA10759, K59298921, openSUSE-SU-2016:2391-1, openSUSE-SU-2016:2407-1, openSUSE-SU-2016:2537-1, openSUSE-SU-2018:0458-1, RHSA-2016:1940-01, SA132, SB10215, SOL59298921, SP-CAAAPUE, SPL-129207, SSA:2016-266-01, SUSE-SU-2016:2387-1, SUSE-SU-2016:2394-1, SUSE-SU-2016:2458-1, SUSE-SU-2016:2468-1, SUSE-SU-2016:2469-1, TNS-2016-16, USN-3087-1, USN-3087-2, VIGILANCE-VUL-20458.

Description of the vulnerability

The OpenSSL library implements DTLS (Datagram Transport Layer Security, for example on UDP).

In order to manage replays, OpenSSL uses a sliding window containing accepted sequence numbers. However, if an attacker sends a packet with a large sequence number, the window is moved, and legitimate packets thus have numbers before the beginning of the window, and are rejected.

An attacker can therefore send a DTLS packet with a large sequence number to an application compiled with OpenSSL, in order to trigger a denial of service.
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