Google discloses unpatched Windows zero

CVE-2019-0808 is an elevation-of-privilege flaw in the Windows Win32k kernel component, which fails to properly handle objects in memory, allowing a local, low-privileged attacker to execute code in the kernel and take full control of the system (CVSS 3.1: 7.8, high impact on confidentiality, integrity and availability). It is triggered by a local attacker running crafted actions against vulnerable Win32k system calls; a public proof of concept based on the NtUserMNDragOver call path is available. Per the source data, affected products are Windows 7 and Windows Server 2008 (exact service-pack/version ranges are not specified in the data). The bug was one of two Win32k zero-days patched in the March 2019 Patch Tuesday, was being actively exploited in targeted attacks attributed to the FruityArmor and SandCat groups, and Microsoft followed with an out-of-band fix after Google disclosed the zero-day. It is listed in CISA KEV (added 2021-11-03, ransomware use unknown), and EPSS currently assigns roughly a 53% probability of exploitation within 30 days (99th percentile).

Do: Apply the March 2019 Microsoft security updates (or the out-of-band fix) for Windows 7 and Windows Server 2008, including Extended Security Updates for systems past the January 2020 end of support, per the CISA KEV required action. Prioritize shared/terminal and RDS hosts where low-privileged users log in, since successful exploitation grants kernel-level privileges, and review those systems for indicators of the FruityArmor/SandCat targeted intrusions. No reliable workaround is documented for this Win32k flaw, so patching is the primary mitigation.

CVE-2019-5786 is a use-after-free (object lifetime) flaw in Blink, the rendering engine of Google Chrome, fixed in Chrome 72.0.3626.121. A remote attacker triggers it by luring a user to a crafted HTML page, where the stale object allows an out-of-bounds memory access within the renderer process. Successful exploitation produces memory corruption in the browser renderer — scored in the CVSS vector primarily as high availability impact — and Google disclosed the flaw being actively exploited in targeted attacks, reportedly chained with a separate Windows zero-day that Microsoft patched out of band in March 2019. Anyone running Chrome older than 72.0.3626.121 was affected, which at disclosure time meant a large share of Chrome's billion-plus desktop user base. Exploitation is confirmed in the wild: the issue was a zero-day before the patch, it was added to CISA's Known Exploited Vulnerabilities catalog on 2022-05-23, and EPSS assigns a ~61.5% probability of exploitation within 30 days (99th percentile).

Do: Update Chrome to 72.0.3626.121 or later — verify via the browser's About/Settings help page and relaunch any pending auto-update, since Chrome self-updates but requires a relaunch. Treat as a KEV priority and patch per vendor instructions, and apply Microsoft's March 2019 updates, including the out-of-band Windows fix, because the Chrome flaw was used in combination with a Windows zero-day in the observed targeted attacks.

Google Chrome bundles the open-source FreeType library for font rendering, and that library contains a heap buffer overflow (CWE-787, out-of-bounds write) in its Load_SBit_Png function. The flaw is triggered when the browser loads a crafted font containing a malicious PNG image embedded as embedded bitmap data, typically from a web page the victim visits, corrupting heap memory with attacker-controlled data. Successful exploitation can crash the browser or execute code in the renderer, and it was used in the wild as part of an exploit chain combined with CVE-2020-17087 (Windows kernel) and CVE-2020-16010 (Android) to escape the sandbox. Anyone running an affected Google Chrome release that ships the vulnerable FreeType code, across Windows, macOS, Linux, Chrome OS and Android, is affected, meaning effectively the entire Chrome install base at the time of disclosure. The vulnerability is confirmed exploited in the wild (listed in CISA's KEV catalog, added 2021-11-03; ransomware use unknown), Google patched it in Chrome 86.0.4240.111, no public proof-of-concept is known, and EPSS estimates a 44.3% probability of exploitation within 30 days (99th percentile).

Do: Update Google Chrome to 86.0.4240.111 or later (any current stable-channel release satisfies this), and where other software bundles FreeType directly, update to FreeType 2.10.4 or later per the upstream fix. Because the bug was chained with CVE-2020-17087 on Windows and CVE-2020-16010 on Android, also apply the corresponding Microsoft Windows and Android updates to close the sandbox-escape chain. Use endpoint management to inventory browser versions and confirm no endpoints remain below the fixed release, as required by the CISA KEV catalog.

CVE-2020-17087 is a local elevation-of-privilege flaw in the Windows kernel caused by an incorrect buffer size calculation (CWE-131), producing a kernel buffer overflow; public analyses from Microsoft and Google's disclosure place the vulnerable code in the kernel's cryptographic driver (cng.sys). A local attacker with low privileges can trigger the overflow without user interaction, gaining code execution in kernel context and effectively full control of the host (high impact on confidentiality, integrity, and availability; CVSS 7.8). Every Windows system on the affected builds is exposed: Windows 10 versions 1507 through 20H2, Windows 7, 8.1, RT 8.1, and Windows Server 2008, which at disclosure meant essentially the entire supported Windows install base. The flaw was exploited as a zero-day in the wild: Google disclosed its use in targeted attacks, reportedly chained with a Chrome zero-day, and CISA added it to the KEV catalog on 2021-11-03; EPSS currently estimates a 5.4% probability of exploitation within 30 days (92nd percentile), with ransomware association listed as unknown.

Do: Apply Microsoft's November 2020 Patch Tuesday security updates to all affected Windows 10, Windows 7, 8.1, RT 8.1, and Windows Server 2008 systems; this is CISA's required action for the KEV listing and no official workaround is known. Prioritize hosts where untrusted users can log on locally or via RDP, and ensure Chromium-based browsers are fully updated since this kernel bug was reportedly chained with a Chrome zero-day. After patching, verify the November 2020 update is installed; treat any ransomware association as currently unconfirmed.