CVE-2021-21206
Google Chromium Blink Use-After-Free Vulnerability
Description
CVE-2021-21206 is a high-severity use after free vulnerability affecting Google Chromium Blink. Google Chromium Blink contains a use-after-free vulnerability that allows a remote attacker to potentially exploit heap corruption via a crafted HTML page. This vulnerability could affect multiple web browsers that utilize Chromium, including Google Chrome, Microsoft Edge, and Opera. CISA has added this vulnerability to its Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. With an EPSS score of 21.91% (95.7th percentile), this vulnerability has a significant probability of exploitation.
KEV Information
CVSS Score
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:HOpen in CalculatorAffected Products
| Vendor | Product | Version |
|---|---|---|
| chrome | < 89.0.4389.128 | |
| fedoraproject | fedora | 32; 33; 34 |
Multiple CVSS Assessments
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
References
- https://chromereleases.googleblog.com/2021/04/stable-channel-update-for-desktop.html(Release Notes)
- https://crbug.com/1196781(Permissions Required, Third Party Advisory)
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EAJ42L4JFPBJATCZ7MOZQTUDGV4OEHHG/(Release Notes)
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/U3GZ42MYPGD35V652ZPVPYYS7A7LVXVY/(Release Notes)
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VUZBGKGVZADNA3I24NVG7HAYYUTOSN5A/(Release Notes)
- https://security.gentoo.org/glsa/202104-08(Third Party Advisory)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-21206(US Government Resource)
Weakness Type
CWE-416: Use After Free
Use After Free (UAF) is a vulnerability that 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.
Learn more: CWE-416 — Use After Free
Impact Analysis
CVE-2021-21206 carries a CVSS 3.1 score of 8.8 (HIGH), indicating a high-severity threat. The vulnerability is exploitable over the network with low attack complexity and requires no authentication, though user interaction is needed. Successful exploitation can severely compromise data confidentiality, and allow unauthorized modification of data and systems, and cause complete service disruption. Organizations running affected Chromium-based browsers face significant operational risk if this vulnerability remains unpatched.
Exploit Maturity
CVE-2021-21206 is confirmed as actively exploited through its listing in the CISA Known Exploited Vulnerabilities catalog. The EPSS score of 21.91% (95.7th percentile) indicates a significant probability of exploitation. The vulnerability affects a widely deployed browser engine, increasing the pool of potential targets. Federal agencies were required to remediate this vulnerability by 2021-11-17 per CISA's binding operational directive.
Remediation
- Apply vendor patches immediately as mandated by CISA KEV: Apply updates per vendor instructions.
- Update all Chromium-based browsers (Google Chrome, Microsoft Edge, Opera, and others) to the latest stable version that addresses this vulnerability.
- If immediate patching is not possible, restrict access to untrusted web content and consider disabling the affected browser component where feasible.
- Monitor systems for indicators of compromise, including unusual process activity, unexpected network connections, and unauthorized configuration changes.
- Review security logs and conduct threat hunting to determine if the vulnerability was exploited prior to patching.
Technical Details
CVE-2021-21206 affects Google Chromium Blink. Use after free in Blink in Google Chrome prior to 89.0.4389.128 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page. The attack vector is network-based, meaning an attacker can exploit this vulnerability remotely by luring a victim to visit a specially crafted webpage. The CVSS score of 8.8 reflects the combination of low attack complexity, no required privileges, and high impact across confidentiality, integrity, availability.
Frequently Asked Questions
Is CVE-2021-21206 being actively exploited?
Yes. CVE-2021-21206 is listed in the CISA Known Exploited Vulnerabilities catalog, confirming active exploitation. The EPSS score of 21.91% (95.7th percentile) further indicates a significant exploitation probability.
What products are affected by CVE-2021-21206?
CVE-2021-21206 affects Google Chromium Blink. Since the vulnerability resides in the Chromium engine, multiple browsers that utilize Chromium may be affected, including Google Chrome, Microsoft Edge, and Opera.
How do I fix CVE-2021-21206?
Apply updates per vendor instructions. Ensure all Chromium-based browsers are updated to the latest patched versions. If patching is not immediately possible, implement network-level mitigations to limit exposure to untrusted web content.
How severe is CVE-2021-21206?
CVE-2021-21206 has a CVSS 3.1 score of 8.8 (HIGH). This is a high-severity vulnerability that requires immediate attention and remediation.
Need Help With Vulnerability Management?
Our security experts can help you prioritize and remediate vulnerabilities effectively.