{"id":35396,"date":"2019-10-31T22:04:04","date_gmt":"2019-10-31T19:04:04","guid":{"rendered":"https:\/\/prohoster.info\/blog\/uyazvimosti-v-tcp-stekah-linux-i-freebsd-privodyashhie-k-udalyonnomu-otkazu-v-obsluzhivanii\/"},"modified":"2019-10-31T22:04:04","modified_gmt":"2019-10-31T19:04:04","slug":"uyazvimosti-v-tcp-stekah-linux-i-freebsd-privodyashhie-k-udalyonnomu-otkazu-v-obsluzhivanii","status":"publish","type":"post","link":"https:\/\/prohoster.info\/en\/blog\/news\/uyazvimosti-v-tcp-stekah-linux-i-freebsd-privodyashhie-k-udalyonnomu-otkazu-v-obsluzhivanii","title":{"rendered":"Vulnerabilities in the TCP stacks of Linux and FreeBSD leading to remote denial of service.","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Netflix Company has identified<\/a><\/noindex> several critical vulnerabilities<\/a><\/noindex> in TCP stacks of Linux and FreeBSD that allow remote initiation of a kernel crash or cause excessive resource consumption when processing specially crafted TCP packets (packet-of-death). The issues are caused by<\/a><\/noindex> errors in the maximum segment size (MSS, Maximum Segment Size) handlers and the selective acknowledgment (SACK, TCP Selective Acknowledgement) mechanism.<\/p>\n

  • CVE-2019-11477<\/a><\/noindex> (SACK Panic) \u2014 This issue appears in Linux kernels starting from 2.6.29 and allows a kernel panic to be triggered by sending a series of SACK packets due to an integer overflow in the handler. To execute the attack, it is sufficient to set the MSS value for a TCP connection to 48 bytes (the lower limit, which sets the segment size to 8 bytes) and send a sequence of specifically crafted SACK packets.\n

    As a workaround for protection, SACK processing can be disabled (by setting 0 in \/proc\/sys\/net\/ipv4\/tcp_sack) or block<\/a><\/noindex> connections with low MSS (works only when the sysctl net.ipv4.tcp_mtu_probing is set to 0 and may disrupt the operation of some normal connections with low MSS);<\/p>\n

  • CVE-2019-11478<\/a><\/noindex> (SACK Slowness) \u2014 This leads to a disruption of the SACK mechanism (when using Linux kernels older than 4.15) or excessive resource consumption. The problem arises during the processing of specially crafted SACK packets, which can be used to fragment the TCP retransmission queue. Mitigation strategies are similar to the previous vulnerability.\n
  • CVE-2019-5599<\/a><\/noindex> (SACK Slowness) \u2014 This allows an attacker to cause fragmentation of the sent packets map when processing a specific sequence of SACK within a single TCP connection, leading to a resource-intensive listing operation. The issue manifests in FreeBSD 12 with the RACK packet loss detection mechanism. As a workaround, the RACK module can be disabled.\n
  • CVE-2019-11479<\/a><\/noindex> \u2014 An attacker can cause the Linux kernel to split responses into multiple TCP segments, each containing only 8 bytes of data, which can lead to a significant increase in traffic, increased CPU load, and congestion in the communication channel. As a protective workaround, it is recommended to block<\/a><\/noindex> use connections with low MSS.\n<\/ul>\n

    In the Linux kernel, the issues have been fixed in releases 4.4.182, 4.9.182, 4.14.127, 4.19.52, and 5.1.11. A fix for FreeBSD is available as a patch<\/a><\/noindex>In the distributions, updates for the kernel packages have already been released for Debian<\/a><\/noindex>, SUSE\/openSUSE<\/a><\/noindex>, Arch<\/a><\/noindex>A fix is being prepared for Ubuntu<\/a><\/noindex>, Alpine<\/a><\/noindex> and Arch Linux<\/a><\/noindex>.<\/p>\n

    <\/a><\/noindex><\/p>\n

    Source: opennet.ru<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

    \u041a\u043e\u043c\u043f\u0430\u043d\u0438\u044f Netflix \u0432\u044b\u044f\u0432\u0438\u043b\u0430 \u043d\u0435\u0441\u043a\u043e\u043b\u044c\u043a\u043e \u043a\u0440\u0438\u0442\u0438\u0447\u0435\u0441\u043a\u0438\u0445 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0435\u0439 \u0432 TCP-\u0441\u0442\u0435\u043a\u0430\u0445 Linux \u0438 FreeBSD, \u043a\u043e\u0442\u043e\u0440\u044b\u0435 \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0442 \u0443\u0434\u0430\u043b\u0451\u043d\u043d\u043e \u0438\u043d\u0438\u0446\u0438\u0438\u0440\u043e\u0432\u0430\u0442\u044c \u043a\u0440\u0430\u0445 \u044f\u0434\u0440\u0430 \u0438\u043b\u0438 \u0432\u044b\u0437\u0432\u0430\u0442\u044c \u0447\u0440\u0435\u0437\u043c\u0435\u0440\u043d\u043e\u0435 \u043f\u043e\u0442\u0440\u0435\u0431\u043b\u0435\u043d\u0438\u0435 \u0440\u0435\u0441\u0443\u0440\u0441\u043e\u0432 \u043f\u0440\u0438 \u043e\u0431\u0440\u0430\u0431\u043e\u0442\u043a\u0435 \u0441\u043f\u0435\u0446\u0438\u0430\u043b\u044c\u043d\u043e \u043e\u0444\u043e\u0440\u043c\u043b\u0435\u043d\u043d\u044b\u0445 TCP-\u043f\u0430\u043a\u0435\u0442\u043e\u0432 (packet-of-death). \u041f\u0440\u043e\u0431\u043b\u0435\u043c\u044b \u0432\u044b\u0437\u0432\u0430\u043d\u044b \u043e\u0448\u0438\u0431\u043a\u0430\u043c\u0438 \u0432 \u043e\u0431\u0440\u0430\u0431\u043e\u0442\u0447\u0438\u043a\u0430\u0445 \u043c\u0430\u043a\u0441\u0438\u043c\u0430\u043b\u044c\u043d\u043e\u0433\u043e \u0440\u0430\u0437\u043c\u0435\u0440\u0430 \u0431\u043b\u043e\u043a\u0430 \u0434\u0430\u043d\u043d\u044b\u0445 \u0432 TCP-\u043f\u0430\u043a\u0435\u0442\u0435 (MSS, Maximum segment size) \u0438 \u043c\u0435\u0445\u0430\u043d\u0438\u0437\u043c\u0430 \u0432\u044b\u0431\u043e\u0440\u043e\u0447\u043d\u043e\u0433\u043e \u043f\u043e\u0434\u0442\u0432\u0435\u0440\u0436\u0434\u0435\u043d\u0438\u044f \u0441\u043e\u0435\u0434\u0438\u043d\u0435\u043d\u0438\u0439 (SACK, TCP Selective Acknowledgement). CVE-2019-11477 (SACK Panic) […]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[],"class_list":["post-35396","post","type-post","status-publish","format-standard","hentry","category-news"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\n","aioseo_head_json":{"title":"\ud83e\udd47Vulnerabilities in the TCP stacks of Linux and FreeBSD, leading to remote denial of service | ProHoster","description":"Netflix has identified several 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