CVE-2026-11186 in Chrome
Summary
by MITRE • 06/05/2026
Inappropriate implementation in CSS in Google Chrome prior to 149.0.7827.53 allowed a remote attacker to inject arbitrary scripts or HTML (UXSS) via a crafted HTML page. (Chromium security severity: Medium)
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Analysis
by VulDB Data Team • 06/05/2026
This vulnerability represents a cross-site scripting issue within Google Chrome's CSS processing engine that existed prior to version 149.0.7827.53. The flaw stems from insufficient input validation and sanitization within the browser's stylesheet handling mechanisms, specifically when processing crafted HTML content that includes malicious CSS directives. The vulnerability manifests as an unauthorized script injection vector that allows remote attackers to execute arbitrary code within the context of the victim's browser session. The technical implementation error occurs when Chrome's rendering engine fails to properly escape or validate CSS content that originates from untrusted sources, creating a path for malicious payloads to bypass standard security boundaries. This issue falls under the CWE-79 category for Cross-Site Scripting, specifically representing a variant where the attack vector originates through CSS processing rather than traditional HTML injection points. The vulnerability enables an attacker to construct malicious web pages that, when viewed by victims, can execute unauthorized scripts or inject additional HTML content into the page. The medium severity classification reflects the fact that while the attack requires user interaction through visiting a malicious page, the potential impact includes complete session hijacking and arbitrary code execution. The exploitability requires the attacker to craft a specific HTML page containing malicious CSS that can trigger the vulnerable code path during page rendering. This particular implementation flaw demonstrates a failure in the browser's content security model where CSS processing does not adequately isolate potentially malicious content from the main execution environment.
The operational impact of this vulnerability extends beyond simple script execution to encompass complete browser compromise and user session takeover capabilities. Attackers can leverage this vector to steal cookies, modify page content, redirect users to malicious sites, or perform actions on behalf of authenticated users. The UXSS (User eXecution) nature of this vulnerability means that the attack succeeds even when users visit legitimate sites that have been compromised through other attack vectors, as the malicious CSS can be injected into otherwise trusted domains. This creates a particularly dangerous scenario where users may be vulnerable to attacks even when browsing secure websites. The vulnerability's exploitation requires no special privileges or local access, making it particularly concerning for widespread deployment. Organizations using affected Chrome versions face increased risk of targeted attacks and credential theft, with the potential for extended session hijacking and data exfiltration. The attack surface includes web applications that may inadvertently process user-supplied CSS content or that rely on Chrome's default security settings without additional protections.
Mitigation strategies for this vulnerability focus on immediate browser updates to the patched version 149.0.7827.53 or later, which incorporates proper input validation and sanitization within the CSS processing pipeline. Organizations should implement comprehensive browser hardening policies including the deployment of Content Security Policy headers to limit script execution and prevent unauthorized content injection. Network-level protections such as web application firewalls and proxy configurations can provide additional layers of defense by filtering suspicious CSS content and monitoring for known malicious patterns. Security teams should conduct regular vulnerability assessments to identify potentially vulnerable web applications that may be susceptible to similar attacks through user input processing. Browser security configurations should be reviewed to ensure that automatic updates are enabled and that users are not bypassing security features. The implementation of strict input validation for all CSS content, particularly when processing user-generated material, serves as a critical defensive measure. Additionally, security monitoring should include detection of unusual CSS processing patterns and potential attempts to exploit similar vulnerabilities in other browser components. Organizations should maintain updated threat intelligence feeds to identify new attack patterns targeting this class of vulnerability and ensure their security tools can detect and block malicious CSS injection attempts. The vulnerability underscores the importance of comprehensive security testing across all browser rendering components and the necessity of maintaining up-to-date security patches to protect against evolving attack vectors.