A flaw in the way reply ICMP packets are limited in the Linux kernel functionality was found that allows to quickly scan open UDP ports. This flaw allows an off-path remote user to effectively bypassing source port UDP randomization. The highest threat from this vulnerability is to confidentiality and possibly integrity, because software that relies on UDP source port randomization are indirectly affected as well. Kernel versions before 5.10 may be vulnerable to this issue.

References

• https://nvd.nist.gov/vuln/detail/CVE-2020-25705
• https://bugzilla.redhat.com/show_bug.cgi?id=1894579
• https://cert-portal.siemens.com/productcert/pdf/ssa-324955.pdf
• https://lists.debian.org/debian-lts-announce/2020/12/msg00015.html
• https://lists.debian.org/debian-lts-announce/2020/12/msg00027.html
• https://security.netapp.com/advisory/ntap-20201210-0002/
• https://us-cert.cisa.gov/ics/advisories/icsa-21-131-03