PSIRT Advisory

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.

Impact

Information disclosure

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

For FortiAnalyzer, upgrade to version

• 5.4.2 

References

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