VulnerabilityPublished 28 Sep 2026

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

Affects @angular/platform-serverSource GCVE Database

Not known to be exploited · CVSS 8.6 High : upgrade to 22.1.4 soon.

Data as of 26 Oct 2026, 13:47 UTC

CVSS 4.0 base score

8.6High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.2% chance of exploitation in 30 days – higher than 20% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 22.1.4, 21.2.22, 20.3.30

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: Passive
Vulnerable system confidentiality: High
Vulnerable system integrity: High
Vulnerable system availability: None
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: Passive: Successful exploitation of this vulnerability requires limited interaction by the targeted user with the vulnerable system and the attacker’s payload. These interactions would be considered involuntary and do not require that the user actively subvert protections built into the vulnerable system.
Vulnerable system confidentiality: High: There is a total loss of confidentiality, resulting in all information within the Vulnerable System being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.
Vulnerable system integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the vulnerable system. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the vulnerable system.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 28 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade @angular/platform-server to 22.1.4; @angular/platform-server to 21.2.22; @angular/platform-server to 20.3.30.

Affected software

Product	Affected	Fixed in
npm@angular/platform-server	Affected >=22.0.0 <22.1.4	Fixed in 22.1.4
npm@angular/platform-server	Affected >=21.0.0 <21.2.22	Fixed in 21.2.22
npm@angular/platform-server	Affected >=20.0.0 <20.3.30	Fixed in 20.3.30
npm@angular/platform-server	Affected <=19.2.25	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

### Summary An XSS vulnerability exists in `@angular/platform-server` during server-side rendering (SSR) HTML serialization of `ProcessingInstruction` DOM nodes (`<?target data?>`, `nodeType === 7`) when nested inside fallback raw-content elements (`<noscript>`, `<iframe>`, `<noembed>`, `<noframes>`). While processing instruction data escaped `>` to `>`, it did not check for or escape matching closing tags of ancestor fallback elements (e.g., `</noscript>`). When rendered in a browser with scripting enabled, an unescaped closing tag sequence in a processing instruction prematurely closes the fallback raw-content tag and causes subsequent sibling elements to execute as live HTML. ### Technical Description In HTML5 parsing, fallback raw-content elements (`<noscript>`, `<iframe>`, `<noembed>`, `<noframes>`) place the browser's HTML tokenizer into `RAWTEXT` mode. In `RAWTEXT` mode, processing instruction tokens (`<?...?>`) are treated as literal raw text rather than bogus comments, and the parser ignores `>` or `?>`. The only token sequence that terminates the container is an end tag matching the container tag name (`</noscript`, `</iframe`, etc.). During server-side HTML serialization, processing instruction nodes previously only replaced `>` with `>` (preventing bogus comment breakouts in normal HTML data states) but left `<` untouched. Crucially, processing instruction serialization never inspected ancestor fallback raw-content tags. As a result, if a `ProcessingInstruction` node inside `<noscript>` contained `</noscript ` in its data payload, it was emitted unescaped as `<?x </noscript ?>`. ### Impact & Reachability * **Reachability**: Processing instruction nodes cannot be authored directly through standard Angular template syntax (which parses `<?...>` into comment nodes in DOM position). Reaching this vulnerability requires application or library code calling `inject(DOCUMENT).createProcessingInstruction(target, data)` or `Renderer2` DOM insertion methods with untrusted user input passed to `data` inside a fallback raw-content container. * **Impact**: In applications that programmatically construct processing instruction nodes inside fallback elements during server-side rendering, an attacker controlling the processing instruction data can break out of the container and execute arbitrary JavaScript in victims' browsers. ### Proof of Concept (Minimal Reproduction) ```ts import { Component, ElementRef, Renderer2, inject, DOCUMENT, AfterViewInit } from '@angular/core'; @Component({ selector: 'app-root', standalone: true, template: `<noscript id="host"></noscript>` }) export class AppComponent implements AfterViewInit { private r = inject(Renderer2); private el = inject(ElementRef); private doc = inject(DOCUMENT); ngAfterViewInit() { const host = this.el.nativeElement.querySelector('#host'); // Attacker-controlled input passed as Processing Instruction data const pi = this.doc.createProcessingInstruction('x', '</noscript '); this.r.appendChild(host, pi); // Sibling markup that should remain inert inside <noscript> const img = this.r.createElement('img'); this.r.setAttribute(img, 'src', 'x'); this.r.setAttribute(img, 'onerror', 'alert("SSR_PI_XSS")'); this.r.appendChild(host, img); } } ``` **Vulnerable SSR Output**: ```html <noscript><?x </noscript ?><img src="x" onerror="alert('SSR_PI_XSS')"></noscript> ``` ### Workarounds * Avoid passing untrusted user input into `document.createProcessingInstruction(target, data)` when the node is inserted into `<noscript>`, `<iframe>`, `<noembed>`, or `<noframes>` during server-side rendering. * Manually sanitize or replace `<` with `<` in any untrusted data passed to processing instruction nodes on the server.

CWE-116Improper Encoding or Escaping of Output (opens in a new tab)
Class weaknessLikelihood of exploit: HighOWASP Top 10 A05:2025: Injection (opens in a new tab)
The product prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. As a result, the intended structure of the message is not preserved.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Architecture and Design · Parameterization
If available, use structured mechanisms that automatically enforce the separation between data and code. These mechanisms may be able to provide the relevant quoting, encoding, and validation automatically, instead of relying on the developer to provide this capability at every point where output is generated.
Architecture and Design · Implementation
Understand the context in which your data will be used and the encoding that will be expected. This is especially important when transmitting data between different components, or when generating outputs that can contain multiple encodings at the same time, such as web pages or multi-part mail messages.
OWASP Cheat Sheets
Content Security Policy (opens in a new tab)
Injection Prevention (opens in a new tab)
SQL Injection Prevention (opens in a new tab)
Injection Prevention in Java (opens in a new tab)
Query Parameterization (opens in a new tab)
OWASP ASVS 4.0.3
V14.4.6 (opens in a new tab)
V14.4.4 (opens in a new tab)
V14.4.2 (opens in a new tab)
Attack patterns
Cross Zone Scripting (opens in a new tab)
User-Controlled Filename (opens in a new tab)
Web Server Logs Tampering (opens in a new tab)
AJAX Footprinting (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #1OWASP Top 10 A05:2025: Injection (opens in a new tab)
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Implementation · Architecture and Design
Understand the context in which your data will be used and the encoding that will be expected. This is especially important when transmitting data between different components, or when generating outputs that can contain multiple encodings at the same time, such as web pages or multi-part mail messages.
Architecture and Design · Implementation · Attack Surface Reduction
Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide…
OWASP Cheat Sheets
Cross Site Scripting Prevention (opens in a new tab)
DOM based XSS Prevention (opens in a new tab)
Injection Prevention (opens in a new tab)
Abuse Case (opens in a new tab)
Deserialization (opens in a new tab)
OWASP ASVS 4.0.3
V5.3.3 (opens in a new tab)
V1.5.1 (opens in a new tab)
Attack patterns
XSS Using MIME Type Mismatch (opens in a new tab)
DOM-Based XSS (opens in a new tab)
Reflected XSS (opens in a new tab)
Stored XSS (opens in a new tab)
Cross-Site Scripting (XSS) (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

WeaknessesCWE-116, CWE-79

Technical details

References

Community reviews

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