CVE-2026-87551 in Chrome
Summary
by MITRE • 09/09/2026
Improper certificate validation in CORS in Google Chrome prior to 153.0.8010.36 allowed a remote attacker leveraging social engineering to bypass web origin policy via crafted network traffic. (Chromium security severity: Low)
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 09/09/2026
The vulnerability identified as an improper certificate validation issue within the Cross-Origin Resource Sharing mechanism of Google Chrome prior to version 153.0.8010.36 represents a significant deviation from expected secure browsing behavior. This flaw specifically affects how the browser handles Certificate Transparency logs and SSL/TLS certificates when processing cross-origin requests. In standard web security operations, browsers enforce strict checks on certificate validity to ensure that connections are established with legitimate entities holding valid cryptographic credentials. When this validation process is bypassed or executed incorrectly within the CORS context, it undermines the foundational trust model of HTTPS communications. The Chromium project has classified this issue as having a low severity rating, indicating that while the technical flaw exists, its exploitation requires specific conditions and user interaction to be effective against typical users.
The core technical flaw lies in the browser's handling of network traffic during cross-origin requests where certificate validation is not performed with sufficient rigor. Normally, when a web page attempts to fetch resources from a different origin using methods such as XMLHttpRequest or Fetch API, the browser must verify that the server presenting its SSL/TLS certificate matches the expected domain and possesses valid chain-of-trust credentials. In this specific instance, crafted network traffic could exploit gaps in these checks, allowing an attacker to present certificates that might otherwise be rejected or flagged by standard validation routines. This failure enables a remote attacker to manipulate the perceived origin of content, effectively tricking the browser into treating malicious resources as if they originated from a trusted source. The exploitation relies heavily on social engineering tactics, meaning the victim must be induced to interact with specially crafted network requests or visit compromised sites that trigger these malformed CORS responses.
From an operational impact perspective, this vulnerability facilitates web origin policy bypasses which are critical for maintaining isolation between different websites and applications running in a browser environment. The same-origin policy is designed to prevent malicious scripts on one page from obtaining access to sensitive data such as cookies, session tokens, or DOM elements of another site. By circumventing certificate validation within CORS requests, an attacker could potentially exfiltrate sensitive user data, perform actions on behalf of the authenticated user without consent, or inject malicious content that appears legitimate due to the perceived validity of its source. Although the severity is rated low, the potential for data theft and unauthorized state changes remains a serious concern, particularly in environments where users frequently interact with third-party services or embedded widgets from various origins. The reliance on social engineering suggests that direct automated exploitation at scale may be difficult, but targeted attacks against high-value individuals could still succeed if the user is persuaded to engage with the malicious network traffic.
Mitigation strategies for this vulnerability primarily involve updating the browser software to a version where these certificate validation checks have been corrected and hardened. Users should ensure they are running Google Chrome 153.0.8010.36 or later, as subsequent patches address the specific logic errors in CORS handling that allowed this bypass. Additionally, organizations can implement Content Security Policy headers to restrict which origins are permitted to make cross-origin requests, thereby reducing the attack surface even if a browser vulnerability is present. Monitoring network traffic for anomalous certificate patterns and employing strict SSL pinning where applicable can also provide additional layers of defense against such origin manipulation attempts. It is crucial for security teams to remain vigilant regarding social engineering vectors, as technical controls alone may not prevent users from being tricked into initiating the malicious requests that exploit this flaw.
This incident aligns with common vulnerability classifications found in industry standards, particularly CWE-295 which addresses Improper Certificate Validation. The exploitation technique mirrors tactics observed in ATT&CK framework entries related to Web Protocol Manipulation and potentially Phishing if social engineering is heavily utilized. Understanding these mappings helps security professionals contextualize the risk within broader threat landscapes and prioritize remediation efforts accordingly. By addressing both the technical deficiency in the browser engine and reinforcing user awareness regarding suspicious network interactions, organizations can significantly reduce their exposure to this class of origin bypass vulnerabilities.