CVE-2026-87608 in Chrome
Summary
by MITRE • 09/09/2026
Improper certificate validation in FedCM 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)
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability identified as an improper certificate validation flaw within the FedCM component of Google Chrome prior to version 153.0.8010.36 represents a significant deviation from expected cryptographic verification protocols. Federated Identity Management, or FedCM, is designed to facilitate secure identity federation between websites and identity providers by establishing trusted channels for authentication assertions. The core technical flaw lies in the browser's failure to rigorously validate X.509 certificates during these federated exchanges. Specifically, the implementation allowed network traffic carrying crafted certificate chains to be accepted without proper verification of their authenticity or integrity against a trusted root store. This deficiency effectively neutralizes one of the primary security controls intended to prevent man-in-the-middle attacks and identity spoofing within the federation protocol. By bypassing strict certificate validation, an attacker can manipulate the trust relationship between the relying party website and the identity provider, leading to unauthorized access scenarios that compromise user privacy and account integrity.
From a technical perspective, this flaw aligns with CWE-295, which describes Improper Certificate Validation, as well as CWE-347 regarding Improper Verification of Cryptographic Signature if signature validation was also bypassed due to the certificate failure. The operational impact is primarily driven by social engineering vectors rather than purely automated exploitation techniques. Because the vulnerability requires a remote attacker to leverage crafted network traffic in conjunction with user interaction, it falls under MITRE ATT&CK technique T1566.002, specifically Spearphishing Link or Attachment variants where the link leads to a maliciously configured identity provider endpoint. An adversary could set up a rogue identity provider that presents an invalid or self-signed certificate during the FedCM flow. If Chrome fails to reject this connection based on standard PKI rules, users may be tricked into authenticating through the attacker-controlled service. This results in credential theft or session hijacking, as the browser incorrectly assumes the federation channel is secure and trustworthy.
The severity of this vulnerability is classified as Low by Chromium security standards because it relies heavily on user interaction and social engineering to succeed. It does not allow for direct remote code execution or arbitrary memory corruption but rather facilitates identity-based attacks that require the victim to actively engage with a malicious interface. However, given the critical nature of authentication flows in modern web applications, even low-severity flaws can lead to significant data breaches if exploited at scale through targeted phishing campaigns. The lack of strict certificate validation undermines the zero-trust principles inherent in FedCM implementations, allowing attackers to intercept and potentially alter identity assertions without detection by the browser's security mechanisms.
Mitigation strategies for this vulnerability primarily involve updating Google Chrome to version 153.0.8010.36 or later, where the certificate validation logic has been corrected to enforce strict adherence to PKI standards during FedCM operations. For organizations unable to patch immediately, implementing Content Security Policy headers that restrict connections to known and trusted identity providers can provide a layer of defense against rogue endpoints. Additionally, user education regarding phishing indicators remains crucial since social engineering is the primary delivery mechanism for this exploit. Monitoring network logs for unusual certificate chains or unexpected redirections during authentication flows may also help in detecting attempted exploitation activities before they result in compromise.