CVE-2021-4231Network attack vector

Script injection via incomplete SSR comment escaping

Published May 26, 2022 · Updated Apr 15, 2025

Cross-site scripting in Angular 11.0.0 through 11.0.4 allows remote authenticated users to inject script through server-rendered comments. The escapeCommentText utility neutralizes only the standard comment terminator, so alternate valid delimiters can close an SSR comment before injected markup. Exploitation requires development-mode SSR, attacker-controlled comment reflection, low privileges, and victim interaction; 11.1.0-next.0 through 11.1.0-next.2 is also affected.

CVSS severity3.5
Low
EPSS probability1.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Cross-site scripting in Angular 11.0.0 through 11.0.4 allows remote authenticated users to inject script through server-rendered comments. The escapeCommentText utility neutralizes only the standard comment terminator, so alternate valid delimiters can close an SSR comment before injected markup. Exploitation requires development-mode SSR, attacker-controlled comment reflection, low privileges, and victim interaction; 11.1.0-next.0 through 11.1.0-next.2 is also affected.

The record

CVE
CVE-2021-4231
Published
May 26, 2022
Updated
Apr 15, 2025
Vendor
Angular
Product
Angular
Classifications
CWE-79, T1189
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 26, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 15, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=11.0.0
  2. Affected versionversion=11.0.1
  3. Affected versionversion=11.0.2
  4. Affected versionversion=11.0.3
  5. Affected versionversion=11.0.4
  6. Affected versionversion=11.1.0-next.0
  7. Affected versionversion=11.1.0-next.1
  8. Affected versionversion=11.1.0-next.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Angular · Angularversion=11.0.0; version=11.0.1; version=11.0.2; version=11.0.3; version=11.0.4; version=11.1.0-next.0; version=11.1.0-next.1; version=11.1.0-next.2

Published CVSS scores

3.5CVE ProgramCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
5.4GitHubCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1189Drive-by Compromise

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo