CVE-2026-17851 in Chrome
Summary
by MITRE • 07/30/2026
Side-channel information leakage in Autofill in Google Chrome prior to 151.0.7922.72 allowed a remote attacker who had compromised the renderer process to leak cross-origin data via a crafted HTML page. (Chromium security severity: Medium)
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Analysis
by VulDB Data Team • 07/30/2026
This vulnerability represents a significant side-channel attack vector within Google Chrome's autofill functionality that existed prior to version 151.0.7922.72. The flaw emerged from the improper handling of cross-origin data within the browser's rendering engine, specifically when processing autofill-related operations. Attackers with compromised renderer processes could exploit this weakness by crafting malicious HTML pages that would trigger information leakage mechanisms within Chrome's autofill system.
The technical implementation of this vulnerability stems from insufficient isolation between different origins within Chrome's architecture. When a renderer process executes code from an untrusted origin, the autofill component fails to properly sanitize or restrict access to data that should remain isolated between different websites. This creates a pathway for attackers to observe timing variations or memory access patterns that reveal information about cross-origin resources stored in the browser's autofill database.
The operational impact of this vulnerability extends beyond simple data leakage, as it enables sophisticated reconnaissance attacks where adversaries can gather sensitive information about user accounts, form data, and potentially authentication credentials from other origins. This type of attack aligns with the attack pattern described in the ATT&CK framework under technique T1557 for "Adversary-in-the-Middle" and specifically relates to credential access mechanisms that leverage browser vulnerabilities. The medium severity classification reflects the combination of remote exploitability and the potential for significant data compromise.
The vulnerability demonstrates a clear violation of the principle of least privilege and proper isolation mechanisms that should exist between different browsing contexts within modern browsers. It represents a failure in Chrome's implementation of the same-origin policy enforcement, particularly in how it handles cross-origin resource access through browser features like autofill. This flaw essentially allows attackers to perform covert information gathering that could be used for further exploitation attempts.
Mitigation strategies should focus on implementing proper origin isolation within the autofill system and ensuring that renderer processes cannot observe or infer data from other origins through timing side-channels or memory access patterns. Browser vendors should enforce stricter sanitization of cross-origin data flows, particularly in features that handle sensitive user information. The fix typically involves strengthening the security boundaries between different process contexts and implementing proper input validation to prevent leakage of sensitive information through indirect channels.
This vulnerability type falls under the broader category of side-channel attacks that can be classified as CWE-203 "Information Exposure Through Implementation Error" and specifically relates to CWE-467 "Use of sizeof() on a Pointer Type" or similar memory access pattern issues. The attack vector demonstrates how seemingly benign browser features like autofill can become attack surfaces when proper security boundaries are not maintained, particularly in complex multi-process architectures where different components must maintain strict isolation while still providing necessary functionality to users.
The remediation approach involves comprehensive code review of all cross-origin data handling within the browser's rendering pipeline and implementation of robust timing attack mitigations. Modern browser security practices emphasize the importance of preventing information leakage through any channel, including timing variations that could reveal memory access patterns or data structure characteristics. This vulnerability underscores the critical need for continuous security assessment of browser features that handle sensitive user data, particularly those that operate in multi-process environments where isolation boundaries must be absolutely maintained.