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In res/res_rtp_asterisk.c in Asterisk 11.x before 11.25.2, 13.x before 13.17.1, and 14.x before 14.6.1 and Certified Asterisk 11.x before 11.6-cert17 and 13.x before 13.13-cert5, unauthorized data disclosure (media takeover in the RTP stack) is possible with careful timing by an attacker. The "strictrtp" option in rtp.conf enables a feature of the RTP stack that learns the source address of media for a session and drops any packets that do not originate from the expected address. This option is enabled by default in Asterisk 11 and above. The "nat" and "rtp_symmetric" options (for chan_sip and chan_pjsip, respectively) enable symmetric RTP support in the RTP stack. This uses the source address of incoming media as the target address of any sent media. This option is not enabled by default, but is commonly enabled to handle devices behind NAT. A change was made to the strict RTP support in the RTP stack to better tolerate late media when a reinvite occurs. When combined with the symmetric RTP support, this introduced an avenue where media could be hijacked. Instead of only learning a new address when expected, the new code allowed a new source address to be learned at all times. If a flood of RTP traffic was received, the strict RTP support would allow the new address to provide media, and (with symmetric RTP enabled) outgoing traffic would be sent to this new address, allowing the media to be hijacked. Provided the attacker continued to send traffic, they would continue to receive traffic as well.

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Digium Asterisk Open Source和Certified Asterisk 安全漏洞

Digium Asterisk Open Source和Certified Asterisk都是美国Digium公司的开源电话交换机（PBX）系统软件。该软件支持语音信箱、多方语音会议、交互式语音应答(IVR)等。 Asterisk Open Source和Certified Asterisk中存在安全漏洞。攻击者可利用该漏洞劫持目标媒体的会话。以下产品和版本受到影响：Asterisk Open Source 11.25.2之前的11.x版本，13.17.1之前的13.x版本，14.6.1之前的14.x版

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