K37451543 : TMM vulnerability CVE-2021-23007

Security Advisory Description

When the Traffic Management Microkernel (TMM) process handles certain undisclosed traffic, it may start dropping all fragmented IP traffic. (CVE-2021-23007)

Impact

TMM incorrectly determines that the fragment memory limit has been reached and drops all fragments it receives, disrupting traffic to the BIG-IP system.

You can determine if your system is impacted by running the tmctl ip_stat command from the BIG-IP command line and reviewing the output for an unusually large value in thefrag_bytes_used column for a given TMM. You may observe that some TMM processes have high values and others do not. For example:

   rx_frag rx_frag_dropped err_frag_mem_limit_reached      frag_bytes_used
  -------- --------------- -------------------------- --------------------
  46406517             508                          0                    0

   rx_frag rx_frag_dropped err_frag_mem_limit_reached      frag_bytes_used
  -------- --------------- -------------------------- --------------------
  44739031             217                          0                    0

   rx_frag rx_frag_dropped err_frag_mem_limit_reached      frag_bytes_used
  -------- --------------- -------------------------- --------------------
  39322744         8404728                    8404628 18446744073709547072

   rx_frag rx_frag_dropped err_frag_mem_limit_reached      frag_bytes_used
  -------- --------------- -------------------------- --------------------
  33528060        15659496                   15659334 18446744073709547072

   rx_frag rx_frag_dropped err_frag_mem_limit_reached      frag_bytes_used
  -------- --------------- -------------------------- --------------------
  46712180             157                          0                    0

   rx_frag rx_frag_dropped err_frag_mem_limit_reached      frag_bytes_used
  -------- --------------- -------------------------- --------------------
  38912369        10588696                   10588558 18446744073709547072