CVE-2026-101897 in Angular
Summary
by MITRE • 10/15/2026
Angular is a development platform for building mobile and desktop web applications using TypeScript/JavaScript and other languages. From 1.20.0 until 1.21.1, the Angular DevTools background service worker accepts chrome.runtime.sendMessage runtime messages from untrusted web pages or third-party content scripts without adequately verifying the message source. An untrusted sender that obtains a valid randomized victim tabId can direct the extension to use chrome.debugger to attach to another browser tab and trigger Chrome DevTools Protocol breakpoints. This can display the debugging banner, pause JavaScript execution, and prevent interaction with the target tab, but it does not provide remote code execution, privilege escalation, or cross-origin access to memory or credentials. This issue is fixed in version 1.21.1.
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Analysis
by VulDB Data Team • 10/18/2026
The Angular DevTools extension serves as a critical utility for developers working within the Angular framework, providing enhanced debugging capabilities and insights into application performance. However, versions ranging from 1.20.0 to 1.21.1 contained a significant security flaw in their background service worker architecture. This component is responsible for handling communication between the extension's user interface and its internal logic, including interactions with the Chrome browser API. The vulnerability stems from an insufficient validation of message sources when processing chrome.runtime.sendMessage calls. Specifically, the service worker failed to adequately verify that incoming messages originated solely from trusted parts of the extension itself, rather than accepting inputs from untrusted web pages or third-party content scripts injected into other tabs. This lack of strict origin checking creates a pathway for malicious actors to manipulate the extension's behavior by sending crafted runtime messages.
The operational impact of this vulnerability allows an attacker who can inject code into any browser tab to interact with the Angular DevTools background service worker. By obtaining a valid, randomized victim tabId through enumeration or other means, an untrusted sender can direct the extension to utilize chrome.debugger APIs. This capability enables the attachment of the debugger interface to another specific browser tab without user consent for that particular action. Once attached, the attacker can trigger Chrome DevTools Protocol breakpoints within the target application's JavaScript execution context. The immediate result is the display of a debugging banner and the pausing of JavaScript execution on the targeted page. This effectively creates a denial-of-service condition for the victim by freezing their interaction with the web application, preventing them from clicking buttons, submitting forms, or navigating further until the debugger is detached or the tab is refreshed.
It is crucial to distinguish this vulnerability from more severe classes such as remote code execution or cross-site scripting that might lead to data exfiltration. The attack vector described does not grant the attacker direct access to read memory contents, steal credentials stored in local storage or cookies, or escalate privileges within the browser sandbox. The primary consequence is a disruption of service and potential privacy leakage through side-channel observations if an observer could monitor the debugger attachment events, though the core exploit focuses on execution control rather than data theft. This behavior aligns with CWE-20 Improper Input Validation, as the root cause lies in the failure to restrict input sources for critical API calls. Furthermore, from a threat modeling perspective using MITRE ATT&CK techniques, this vulnerability facilitates Initial Access and Execution phases by allowing an attacker to hijack debugging tools to disrupt user sessions or potentially use the debugger interface for further reconnaissance if other vulnerabilities were present in conjunction with this flaw.
The issue was addressed in version 1.21.1 of Angular DevTools through rigorous input validation improvements within the background service worker. The fix ensures that chrome.runtime.sendMessage handlers now strictly verify the origin and integrity of incoming messages, rejecting any attempts from untrusted contexts such as arbitrary web pages or injected content scripts. For organizations still utilizing older versions of the extension, immediate mitigation involves upgrading to version 1.21.1 or later. In environments where automatic updates are not feasible, administrators should enforce policies that restrict the installation of browser extensions and monitor for unauthorized debugger attachments using endpoint detection and response tools capable of logging chrome.debugger API usage. Regular auditing of installed extensions against known vulnerability databases remains essential to maintain a secure development environment.