Bob Huber, chief security officer of cyber security firm Tenable, said the decision was "a bad move, plain and simple".
"By relying on CVSSv3 ratings alone, Microsoft is eliminating a ton of valuable vulnerability data that can help inform organisations of the business risk a particular flaw poses to them," he said.
The decision was announced on Monday US time, with the software behemoth issuing a blog post claiming that "With the launch of the new version of the Security Update Guide, Microsoft is demonstrating its commitment to industry standards by describing the vulnerabilities with the Common Vulnerability Scoring System (CVSS).
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The last time Microsoft made changes to its method of releasing monthly patches was in 2016 when the company decided to release all the patches as one big download, rather than as separate patches.
The practice of releasing all updates, except urgent ones, on a single day was begun in October 2003. As security contractor Debra Littlejohn Shinder put it back in 2016, "The idea was that IT pros could be prepared for the event rather than having to respond “on the fly” with no warning every time a new patch came out.
"Why Tuesday? Well, Mondays are hectic enough already for IT admins who often come in to face issues that have arisen over the weekend. That leaves mid-week, and doing it on Tuesday provides for maximum time to get any problems straightened out before the weekend."
Huber said with the new format, end users would be completely blind to how a particular CVE affected them. "What's more, this makes it nearly impossible to determine the urgency of a given patch. It's difficult to understand the benefits to end-users," he said.
"However, it's not too difficult to see how this new format benefits bad actors. They'll reverse engineer the patches and, by Microsoft not being explicit about vulnerability details, the advantage goes to attackers, not defenders. Without the proper context for these CVEs, it becomes increasingly difficult for defenders to prioritise their remediation efforts.
"While I appreciate that they are adopting the industry-standard format in CVSSv3, Microsoft also must consider that many folks who review Patch Tuesday releases aren't security practitioners. They are the IT counterparts responsible for actually applying the updates who often aren't able (and shouldn't have to) decipher raw CVSS data."
Commenting on the patches released on Tuesday, Tenable staff research engineer Satnam Narang said: "This month's Patch Tuesday includes fixes for 112 CVEs, 17 of which are rated critical. This is a return to form for Microsoft, as the company ended a streak of patching over 100 CVEs last month when they patched 87 CVEs.
"One of the most notable fixes in this month's release is for CVE-2020-17087, an elevation of privilege vulnerability in the Windows Kernel that was exploited in the wild as part of a vulnerability chain with CVE-2020-15999, a buffer overflow vulnerability in the FreeType 2 library used by Google Chrome.
"The elevation of privilege vulnerability was used to escape Google Chrome's sandbox in order to elevate privileges on the exploited system. This is the second vulnerability chain involving a Google Chrome vulnerability and a Windows vulnerability that was exploited in the last year. Chaining vulnerabilities is an important tactic for threat actors.
"While both CVE-2020-15999 and CVE-2020-17087 were exploited in the wild as zero-days, the Cybersecurity and Infrastructure Security Agency published a joint advisory with the FBI last month that highlighted threat actors chaining unpatched vulnerabilities to gain initial access into a target environment and elevate privileges.
"Even though Google and Microsoft have now patched these flaws, it is imperative for organisations to ensure they've applied these patches before threat actors begin to leverage them more broadly."
