The actively exploited Windows spoofing flaw, tracked as CVE-2020-1464 and patched last week by Microsoft, has been known for more than two years, researchers revealed.
Microsoft’s August 2020 Patch Tuesday security updates addressed 120 vulnerabilities, including two zero-days that have been exploited in attacks in the wild.
The two issues are a Windows spoofing bug and a remote code execution flaw in Internet Explorer.
The Windows spoofing flaw, tracked as CVE-2020-1464 can be exploited by an attacker to bypass security features and load improperly signed files. The flaw is related to Windows incorrectly validating file signatures.
“A spoofing vulnerability exists when Windows incorrectly validates file signatures. An attacker who successfully exploited this vulnerability could bypass security features and load improperly signed files.” reads the advisory published by Microsoft.
“In an attack scenario, an attacker could bypass security features intended to prevent improperly signed files from being loaded.”
The flaw affects many Windows OSs, including Windows 7 and Windows Server 2008, for which the IT giant will not provide security updates because the reached the end-of-life.
Microsoft confirmed that threat actors are actively exploiting the issues in attacks against Windows systems but it did not provide technical details about the attacks.
Experts analyzed the code to address the CVE-2020-1464 flaw and discovered that the vulnerability has been known for years and the most serious aspect is that Microsoft was aware of the bug but did not fix it.
According to the security expert Tal Be’ery, the vulnerability, dubbed GlueBall, has been known since August 2018, because a malware sample exploiting it was uploaded to VirusTotal.
Microsoft was informed about the vulnerability after the submission and a blog post published on VirusTotal in January 2019 included technical details about the GlueBall attack.
“Microsoft Windows keeps the Authenticode signature valid after appending any content to the end of Windows Installer (.MSI) files signed by any software developer. This behaviour can be exploited by attackers to bypass some security solutions that rely on Microsoft Windows code signing to decide if files are trusted.” reads the blog post published by Virus Total. “The scenario is especially dangerous when the appended code is a malicious JAR because the resulting file has a valid signature according to Microsoft Windows and the malware can be directly executed by Java.”
In June 2020, experts discovered that the GlueBall issue was exploited in attacks in the wild to deliver malware.
This means that Microsoft did not fix the flaw for some reasons that are still unclear.
“While the technical details are pretty obvious, the way Microsoft had handled the vulnerability report seems rather strange. It was very clear to everyone involved, Microsoft included, that GlueBall is indeed a valid vulnerability exploited in the wild. Therefore, it is not clear why it was only patched now and not two years ago.” wrote Tal Be’ery
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