Low
CVE-2021-24074
CVE-2021-24074
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Technical Analysis
This remains a spectacularly new vulnerability with little documentation associated with it beyond Microsoft’s blog here: https://msrc-blog.microsoft.com/2021/02/09/multiple-security-updates-affecting-tcp-ip/
In the blog, they report that this vulnerability is associated with IPv4 source routing, but the default blocks against source routing on Windows are not suffcient, as the default configuration allows a Windows system to process ICMP requests with source routing.
Reported as a remote code execution vulnerability, Microsoft claims that it will likely not be weaponized for that purpose quickly, though it might see a DoS exploit in the near-term.
There is a patch, but also, the mitigations provided in the guidance (https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-24074) involve the creation of a rule blocking source forwarding from the built-in firewall:
netsh int ipv4 set global sourceroutingbehavior=drop
Such a change in the firewall configuration can be deployed by group policy and would not require a reboot. The rule could also be deployed to infrastructure firewalls, but would then only protect against attacks that took place across the firewall; the rules would need to be set on all Windows system host-based firewalls to protect against lateral movement within a network.
Technical Analysis
Not much to add to @bwatters-r7’s findings but just wanted to note that there is a detailed analysis of this vulnerability now at https://www.armis.com/resources/iot-security-blog/from-urgent-11-to-frag-44-microsoft-patches-critical-vulnerabilities-in-windows-tcp-ip-stack/ and there is also a PoC out that snuck into another blog at the end of https://doar-e.github.io/blog/2021/04/15/reverse-engineering-tcpipsys-mechanics-of-a-packet-of-the-death-cve-2021-24086/ under the Bonus: CVE-2021-24074 section.
CVSS V3 Severity and Metrics
General Information
Vendors
- microsoft
Products
- windows 10 -,
- windows 10 1607,
- windows 10 1803,
- windows 10 1809,
- windows 10 1909,
- windows 10 2004,
- windows 10 20h2,
- windows 7 -,
- windows 8.1 -,
- windows rt 8.1 -,
- windows server 2008 -,
- windows server 2008 r2,
- windows server 2012 -,
- windows server 2012 r2,
- windows server 2016 -,
- windows server 2016 1909,
- windows server 2016 2004,
- windows server 2019 -
