CVE-2026-88058: Angular: SSR XSS via Unescaped Processing Instruction (<?...?>) Nodes in Fallback Raw-Content Elements

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-09-10 · updated 2026-09-29
Weakness: CWE-79

Description

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.

Affected products

angular: from 19.0.0 through 19.2.25; from 20.0.0 before 20.3.30; from 21.0.0 before 21.2.22; from 22.0.0 before 22.1.4 — fixed in 20.3.30, 21.2.22, 22.1.4

How to fix

Upgrade to a fixed version: angular 20.3.30, 21.2.22, 22.1.4. Check the vendor advisory for mitigations.

References

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