Executive brief
a2ui is a web framework that renders UI components based on agent-supplied specifications. The Basic Catalog component accepts regular expression patterns from remote agents and executes them during form validation. An attacker can freeze the user's browser tab by sending a malicious regex pattern that causes excessive backtracking, rendering the application unusable until the browser recovers or the tab is closed.
Technical details
This is a Regular Expression Denial of Service (ReDoS) vulnerability (CWE-1333) in the `regex` validation function of a2ui's Basic Catalog component. The vulnerable code in `basic_catalog/functions/basic_functions.ts` accepts arbitrary regex patterns from agent-supplied specifications and executes them via `new RegExp(pattern).test(value)` without validation or complexity constraints. The regex validation is triggered on every keystroke in bound input fields (TextField), causing catastrophic backtracking on carefully crafted patterns like `(a+)+b`. Attack requires network access to send a malicious component spec; no authentication or user interaction beyond typing is required. An attacker can freeze the renderer's main thread indefinitely, causing complete client-side availability loss. Versions up to 0.10.6 are affected; the issue is tracked in the project but remediation status is unknown.
Affected products
- a2ui-project a2ui up to 0.10.6
Timeline
- 2026-09-15: disclosed
- other: Issue reported on GitHub on 2026-08-17