vulnerability bulletin CVE-2012-4565

Linux kernel: denial of service via TCP Illinois

Synthesis of the vulnerability

When the TCP Illinois congestion control algorithm is enabled, an attacker can monitor TCP statistics, in order to generate a division by zero, which stops the system.
Impacted products: Fedora, Linux, RHEL.
Severity: 1/4.
Creation date: 31/10/2012.
Identifiers: BID-56346, CVE-2012-4565, FEDORA-2012-17462, FEDORA-2012-17479, FEDORA-2012-18691, RHSA-2012:1491-01, RHSA-2012:1580-01, VIGILANCE-VUL-12103.

Description of the vulnerability

The "TCP Illinois" protocol is used to control TCP congestions. It is enabled with:
  sysctl -w net.ipv4.tcp_congestion_control=illinois

The tcp_illinois_info() function of the net/ipv4/tcp_illinois.c file generates usage statistics for TCP Illinois. However, when the TCP socket is used simultaneously, a counter can be set to zero. A division by zero then occurs in the tcp_illinois_info() function.

When the TCP Illinois congestion control algorithm is enabled, an attacker can therefore monitor TCP statistics, in order to generate a division by zero, which stops the system.
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