Google Fixes Exploited Chrome Zero-Day Dropped On Twitter Last Week

Google has released Chrome 90.0.4430.85 to address an actively exploited zero-day and four other high severity security vulnerabilities impacting today’s most popular web browser.

The version released on April 20th, 2021, to the Stable desktop channel for Windows, Mac, and Linux users will be rolling out to all users over the coming weeks.

“Google is aware of reports that exploits for CVE-2021-21224 exist in the wild,” the company’s announcement reads.

PoC dropped on Twitter, zero-day fixed one week later

Google did not share any details on the zero-day besides describing it as a ‘Type Confusion in V8’ and saying that it was reported by VerSprite Inc’s Jose Martinez.

However, Martinez linked it to proof-of-concept (PoC) exploit publicly shared on Twitter one week ago after his initial Chrome Vulnerability Reward Program report from April 5th.

This remote code execution vulnerability cannot be exploited by attackers to escape Chromium’s sandbox security feature (a security feature designed to block exploits from accessing files or executing code on host computers).

However, it can easily be chained with another security bug that can allow the exploit to escape the sandbox and execute arbitrary code on the targeted users’ systems.

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The zero-day PoC for CVE-2021-21224 was dropped on Twitter one day after Google released Chrome 89.0.4389.128 to fix another zero-day bug with a PoC exploit publicly shared two days earlier.

No details on zero-day attacks in the wild

Although Google says that it is aware CVE-2020-16009 active exploitation, the company did not provide any info on the threat actors behind these attacks.

“Access to bug details and links may be kept restricted until a majority of users are updated with a fix,” Google said.

“We will also retain restrictions if the bug exists in a third party library that other projects similarly depend on, but haven’t yet fixed.”

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Google fixed three other high severity vulnerabilities in Chrome 90.0.4430.85:

• CVE-2021-21222: Heap buffer overflow in V8. Reported by Guang Gong of Alpha Lab, Qihoo 360 on 2021-03-30
• CVE-2021-21223: Integer overflow in Mojo. Reported by Guang Gong of Alpha Lab, Qihoo 360 on 2021-04-02
• CVE-2021-21225: Out of bounds memory access in V8. Reported by Brendon Tiszka (@btiszka) supporting the EFF on 2021-04-05
• CVE-2021-21226: Use after free in navigation. Reported by Brendon Tiszka (@btiszka) supporting the EFF on 2021-04