Back in November 2021, the US Cybersecurity and Infrastructure Security Agency (CISA) published the Known Exploited Vulnerabilities (KEV) Catalog to help federal agencies and critical infrastructure organizations identify and remediate vulnerabilities that are actively being exploited. CISA added 548 new vulnerabilities to the catalog across 58 updates from January to end of November 2022, according to Grey Noise in its first-ever "GreyNoise Mass Exploits Report."
Including the approximately 300 vulnerabilities added in November and December 2021, CISA listed approximately 850 vulnerabilities in the first year of the catalog's existence.
Actively exploited vulnerabilities in Microsoft, Adobe, Cisco, and Apple products accounted for over half of the updates to the KEV catalog in 2022, Grey Noise found. Seventy-seven percent of the updates to the KEV catalog were older vulnerabilities dating back to before 2022.
"Many were published in the previous two decades," noted Grey Noise's vice president of data science, Bob Rudis, in the report.
Several of the vulnerabilities in the KEV catalog are from products that have already entered end-of-life (EOL) and end-of-service-life (EOSL), according to an analysis by a team from Cyber Security Works. Even though Windows Server 2008 and Windows 7 are EOSL products, the KEV catalog lists 127 Server 2008 vulnerabilities and 117 Windows 7 vulnerabilities.
"The fact that they are a part of CISA KEV is quite telling as it indicates that many organizations are still using these legacy systems and therefore become easy targets for attackers," CSW wrote in its "Decoding the CISA KEV" report.
Even though the catalog was originally intended for critical infrastructure and public-sector organizations, it has become the authoritative source on which vulnerabilities are – or have been – exploited by attackers. This is key because the National Vulnerability Database (NVD) assigned Common Vulnerabilities and Exposures (CVE) identifiers for over 12,000 vulnerabilities in 2022, and it would be unwieldy for enterprise defenders to assess every single one to identify the ones relevant to their environments. Enterprise teams can use the catalog's curated list of CVEs under active attack to create their priority lists.
In fact, CSW found a bit of a delay between when a CVE Numbering Authority (CNA), such as Mozilla or MITRE, assigned a CVE to a vulnerability and when the vulnerability was added to the NVD. For example, a vulnerability in Apple WebKitGTK (CVE-2019-8720) received a CVE from Red Hat in October 2019 was added to the KEV catalog in March because it was being exploited by BitPaymer ransomware. It had not been added to the NVD as of early November (the cutoff date for CSW's report).
An organization relying on the NVD to prioritize patching would miss issues that are under active attack.
Thirty-six percent of the vulnerabilities in the catalog are remote code execution flaws and 22% are privilege execution flaws, CSW found. There were 208 vulnerabilities in CISA’s KEV Catalog associated with ransomware groups and 199 being used by APT groups, CSW found. There was an overlap, as well, where 104 vulnerabilities were being used by both ransomware and APT groups.
For instance, a medium-severity information disclosure vulnerability in Microsoft Silverlight (CVE-2013-3896) is associated with 39 ransomware groups, CSW said. The same analysis from CSW found that a critical buffer overflow vulnerability in the ListView/TreeView ActiveX controls used by Office documents (CVE-2012-0158) and a high-severity memory corruption issue in Microsoft Office (CVE-2017-11882) are being exploited by 23 APT groups, including most recently by the Thrip APT group (Lotus Blossom/BitterBug), in November 2022.
The spike in March 2022 is the result of Russia invading Ukraine in February – and the updates included many legacy vulnerabilities that nation-state actors had been known to exploit in businesses, governments, and critical infrastructure organizations, Grey Noise said. The vast majority – 94% – of the vulnerabilities added to the catalog in March were assigned a CVE before 2022.
CISA updates the KEV catalog only if the vulnerability is under active exploitation, has an assigned CVE, and there is clear guidance on how to remediate the issue. In 2022, enterprise defenders had to deal with an update to the KEV catalog on an almost weekly basis, with a new alert typically issued every four to seven days, Rudis wrote. The defenders were just as likely to have just a single day between updates, and the longest break defenders had in 2022 between updates was 17 days.