CVE-2026-88058 in Angular
Summary
by MITRE • 09/10/2026
Angular is a development platform for building mobile and desktop web applications using TypeScript/JavaScript and other languages. Prior to 20.3.30, 21.2.22, and 22.1.4, Angular server-side rendering (SSR) in @angular/platform-server serializes ProcessingInstruction DOM nodes inside fallback raw-content elements without escaping matching ancestor closing tags. ProcessingInstruction data escaped greater-than characters but left less-than characters untouched and did not inspect fallback ancestors, so data such as a matching closing tag prematurely terminates noscript, iframe, noembed, or noframes containers. The vulnerable nodes cannot be authored through standard Angular templates; reachability requires application or library code using inject(DOCUMENT).createProcessingInstruction with attacker-controlled data or Renderer2 DOM insertion inside a fallback container. In HTML5 RAWTEXT parsing, the premature close causes subsequent sibling elements to be interpreted as live HTML and enables arbitrary JavaScript execution in a victim's browser. This issue is fixed in versions 20.3.30, 21.2.22, and 22.1.4.
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Analysis
by VulDB Data Team • 09/10/2026
The vulnerability identified within Angular server-side rendering (SSR) represents a critical input validation failure that occurs during the serialization of ProcessingInstruction DOM nodes into fallback raw-content elements. This flaw is present in specific legacy versions including those prior to 20.3.30, 21.2.22, and 22.1.4. The core technical issue stems from an incomplete sanitization process where the framework correctly escapes greater-than characters but fails to escape less-than characters within ProcessingInstruction data. Furthermore, the serialization logic does not inspect fallback ancestors for matching closing tags. This oversight allows attacker-controlled data containing a closing tag sequence to prematurely terminate HTML5 RAWTEXT containers such as noscript, iframe, noembed, or noframes elements. Because these containers are designed to prevent script execution by treating their content as raw text rather than live markup, breaking out of them effectively disables this security mechanism and re-enables the browser's standard HTML parsing engine for subsequent sibling elements.
The operational impact of this vulnerability is severe, leading directly to Cross-Site Scripting (XSS) attacks in victim browsers. When a ProcessingInstruction node containing malicious data is serialized into one of these raw-content fallbacks, the unescaped less-than character combined with a closing tag sequence causes the browser to interpret subsequent HTML as live code rather than inert text. This allows an attacker to inject arbitrary JavaScript payloads that execute within the context of the victim's session. It is important to note that this vulnerability cannot be triggered through standard Angular template bindings due to their inherent sanitization layers. Instead, reachability requires direct manipulation of the DOM via application or library code using specific APIs such as inject(DOCUMENT).createProcessingInstruction with attacker-controlled input, or the use of Renderer2 for DOM insertion inside a fallback container. This distinction highlights that the risk is primarily associated with advanced usage patterns involving dynamic content generation rather than basic template rendering scenarios.
From an industry standards perspective, this vulnerability aligns closely with CWE-79, which describes Improper Neutralization of Input During Web Page Generation commonly known as Cross-site Scripting. The specific mechanism involves failing to properly encode special characters that have meaning in HTML syntax, specifically the less-than symbol, thereby allowing script injection. In terms of the MITRE ATT&CK framework, this flaw facilitates techniques associated with Client-side Injection and potentially Stored XSS if the malicious ProcessingInstruction data is persisted on the server before being served to clients. The attack vector leverages the browser's parsing behavior in RAWTEXT modes, exploiting the gap between how Angular serializes dynamic content and how browsers interpret that serialized output when containment boundaries are breached.
Mitigation strategies for this vulnerability primarily involve upgrading to patched versions of Angular, specifically version 20.3.30 or later, 21.2.22 or later, and 22.1.4 or later, where the serialization logic has been corrected to properly escape all relevant special characters including less-than signs within ProcessingInstruction nodes. For applications that cannot immediately upgrade, developers should audit codebases for any usage of inject(DOCUMENT).createProcessingInstruction or Renderer2 DOM insertions involving user-controlled data inside fallback containers like noscript or iframe tags. Implementing strict input validation and output encoding at the application layer can provide a secondary defense in depth, ensuring that even if raw content is inserted, it does not contain sequences capable of breaking out of RAWTEXT parsing modes. Additionally, reviewing third-party libraries for similar patterns of direct DOM manipulation without adequate sanitization is recommended to prevent exploitation through indirect code paths.