CVE-2020-16017
Google Chrome Use-After-Free Vulnerability
Description
CVE-2020-16017 is a CRITICAL use-after-free vulnerability in Google Chrome's site isolation component, carrying a CVSS 3.1 score of 9.6. A use-after-free in the site isolation mechanism of Google Chrome prior to version 86.0.4240.198 allows a remote attacker who has compromised the renderer process to potentially perform a sandbox escape via a crafted HTML page. This CVE is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog with a remediation deadline of 2022-05-03. With an EPSS score of 0.21415 (95.622nd percentile), this vulnerability demonstrates very high real-world exploitation activity and was exploited as a zero-day.
KEV Information
CVSS Score
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:HOpen in CalculatorAffected Products
| Vendor | Product | Version |
|---|---|---|
| chrome | < 86.0.4240.198 |
Multiple CVSS Assessments
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
References
- https://chromereleases.googleblog.com/2020/11/stable-channel-update-for-desktop_11.html(Release Notes, Vendor Advisory)
- https://crbug.com/1146709(Permissions Required, Vendor Advisory)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-16017(US Government Resource)
Weakness Type
CWE-416: Use After Free
CVE-2020-16017 is classified under CWE-416 — Use After Free. Use After Free (UAF) occurs when software continues to use a pointer after the memory it references has been freed. Once memory is freed, it may be reallocated for other purposes. If the dangling pointer is subsequently dereferenced, the program may read or write to memory now used for different data structures, leading to data corruption, information disclosure, or code execution.
In the context of Chrome's site isolation mechanism, the use-after-free vulnerability is particularly dangerous because site isolation is itself a security boundary. When this component contains a UAF, attackers who have already achieved renderer compromise can manipulate the freed memory to gain control of the site isolation process, effectively bypassing one of Chrome's key security layers and escaping the renderer sandbox.
Learn more: CWE-416 — Use After Free
Impact Analysis
CVE-2020-16017 carries a CVSS 3.1 score of 9.6 (CRITICAL) with Changed Scope.
Confidentiality (HIGH): Successful sandbox escape allows the attacker to access data beyond the Chrome renderer sandbox, including other application data, user files, and potentially system-level information on the affected device.
Integrity (HIGH): The attacker can modify data outside the renderer sandbox boundary, potentially installing persistent malware, altering system configurations, or compromising other applications on the system.
Availability (HIGH): Complete disruption of the browser and potentially the underlying operating system is possible through the sandbox escape, enabling persistent compromise beyond the browser session.
Scope Changed: The Changed scope is the most critical aspect of this vulnerability. It indicates that exploitation allows breaking out of Chrome's renderer sandbox, impacting the broader operating system environment. This escalation from renderer process to system-level access makes the vulnerability far more dangerous than a renderer-only compromise.
With an EPSS score of 0.21415 (95.622nd percentile), this vulnerability ranks among the most actively exploited, confirmed by its use as a zero-day in the wild.
Exploit Maturity
CVE-2020-16017 has confirmed active exploitation as a zero-day vulnerability and is listed in CISA's Known Exploited Vulnerabilities catalog.
Exploit status: Google confirmed that this vulnerability was being exploited in the wild before a patch was available. The Chrome 86.0.4240.198 release in November 2020 addressed this zero-day along with CVE-2020-16013 (another zero-day in V8). This was part of a series of Chrome zero-days discovered in late 2020.
Ransomware association: No direct ransomware association has been confirmed for CVE-2020-16017. The sandbox escape nature of this vulnerability indicates use in targeted, sophisticated attacks rather than opportunistic ransomware campaigns.
Attack surface: As a sandbox escape vulnerability, CVE-2020-16017 requires that the attacker has already compromised the renderer process through a separate vulnerability. This positions it as a second-stage exploit in a chain, but its presence in Chrome's site isolation component means it undermines one of the browser's most important security features.
KEV deadline: CISA required federal agencies to remediate this vulnerability by 2022-05-03. All organizations should ensure Chrome is updated past version 86.0.4240.198.
Remediation
- Update Google Chrome immediately. Ensure all Chrome installations are updated to version 86.0.4240.198 or later. This applies to Chrome on all desktop platforms (Windows, macOS, Linux).
- Update all Chromium-based browsers. Since the vulnerability is in Chromium's site isolation mechanism, update Microsoft Edge, Opera, Brave, and any other Chromium-based browsers to their corresponding patched versions.
- Enable automatic browser updates organization-wide. Configure managed browser policies to enforce automatic updates, ensuring no devices remain on vulnerable versions.
- Monitor for multi-stage attack indicators. Since this is a sandbox escape requiring prior renderer compromise, monitor for signs of initial exploitation (unusual renderer crashes, suspicious JavaScript execution) as well as post-escape activity (unexpected process creation, file access outside browser directories).
- Implement defense-in-depth at the endpoint level. Deploy endpoint detection and response (EDR) solutions that can detect post-exploitation behavior even when browser sandboxes are bypassed.
- Review site isolation configuration. Ensure site isolation is enabled and properly configured in all managed Chrome installations. While this vulnerability targets the mechanism itself, proper site isolation configuration remains essential for overall browser security.
Technical Details
CVE-2020-16017 is a CRITICAL-severity use-after-free vulnerability in the site isolation component of Google Chrome. The vulnerability enables sandbox escape when exploited by an attacker who has already compromised the renderer process.
Technical mechanism: The use-after-free occurs in Chrome's site isolation implementation, which is responsible for ensuring that pages from different sites are rendered in separate processes. A memory management error in this component causes a pointer to continue referencing freed memory. An attacker who has already achieved code execution in the renderer process can manipulate the heap to place attacker-controlled data in the freed memory region. When the stale pointer is subsequently dereferenced by the site isolation component, the attacker gains control of execution flow in the browser's privileged process, achieving sandbox escape.
Exploit chain context: This vulnerability was discovered alongside other Chrome zero-days in November 2020, including CVE-2020-16013 (V8 type confusion). The typical attack chain would involve a renderer exploit (like a V8 vulnerability) followed by CVE-2020-16017 for sandbox escape, achieving full system compromise.
CVSS 3.1 vector analysis: The vector CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H reflects a network-accessible attack requiring user interaction (visiting a malicious page) with Changed scope (sandbox escape) and HIGH impact across all metrics.
Affected versions: Google Chrome prior to version 86.0.4240.198 on all desktop platforms.
Frequently Asked Questions
Is CVE-2020-16017 being actively exploited?
Yes, CVE-2020-16017 was exploited as a zero-day in the wild before a patch was available. Google confirmed the active exploitation in November 2020 when releasing Chrome 86.0.4240.198. The EPSS score of 0.21415 (95.622nd percentile) confirms very high exploitation probability, and the vulnerability was discovered alongside other Chrome zero-days in a series of sophisticated attacks.
What products are affected by CVE-2020-16017?
Google Chrome prior to version 86.0.4240.198 on desktop platforms is affected. Since the vulnerability exists in the Chromium site isolation component, other Chromium-based browsers (Microsoft Edge, Opera, Brave) may also be affected if running equivalent vulnerable versions. Organizations should update all Chromium-based browsers.
How do I fix CVE-2020-16017?
Update Google Chrome to version 86.0.4240.198 or later on all desktop platforms. Update all other Chromium-based browsers to their corresponding patched versions. Enable automatic updates across managed devices and verify patch deployment through endpoint management tools.
How severe is CVE-2020-16017?
CVE-2020-16017 is rated CRITICAL with a CVSS score of 9.6 and Changed scope, indicating sandbox escape capability. The EPSS score of 0.21415 (95.622nd percentile) confirms extremely high exploitation likelihood. As a confirmed zero-day that enables sandbox escape from Chrome's site isolation mechanism, this vulnerability represents one of the most dangerous types of browser vulnerabilities.
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