Linux kernel - challenge ack information leak

Summary

net/ipv4/tcp_input.c in certain Linux kernel versions does not properly determine the rate of challenge ACK segments, which makes it easier for remote attackers to hijack TCP sessions via a blind in-window attack.

Affected Products

FortiOS versions

• 5.2.8 and below


• 5.4.0 & 5.4.1

FortiAnalyzer versions 5.4.0 & 5.4.1

Solutions

For FortiOS, upgrade to versions

• 5.2.9
• or
• 5.4.2
• or
• 5.6.0
• 5.4.2
• or
• upcoming 5.6.0

References

• https://nvd.nist.gov/vuln/detail/CVE-2016-5696