CVE-2021-4231 is a medium-severity (CVSS 5.4) Cross-site Scripting (XSS) vulnerability in @angular/core. A fix is available for @angular/core — see the affected versions and patch details below.
Angular vulnerable to Cross-site Scripting
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2021-4231.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@angular/corenpmDescription
A vulnerability was found in Angular up to 11.0.4/11.1.0-next.2. It has been classified as problematic. Affected is the handling of comments. The manipulation leads to cross site scripting. It is possible to launch the attack remotely but it might require an authentication first. Upgrading to version 11.0.5 and 11.1.0-next.3 is able to address this issue. The name of the patch is ba8da742e3b243e8f43d4c63aa842b44e14f2b09. It is recommended to upgrade the affected component.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @angular/core | ≥ 11.0.0&&< 11.0.5 | 11.0.5npm install @angular/core@11.0.5 |
| 📦npm | @angular/core | ≥ 11.1.0-next.0&&< 11.1.0-next.3 | 11.1.0-next.3npm install @angular/core@11.1.0-next.3 |
| 📦npm | @angular/core | all versions | 10.2.5npm install @angular/core@10.2.5 |
Affected Products
angularangularangularjsangularjsDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @angular/core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @angular/core to 11.0.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-4231 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This flaw is out of support scope for dotnet-5.0, therefore it will not be addressed in this version of dotnet. For more information, please see https://access.redhat.com/support/policy/updates/net-core.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Ceph Storage 6.1 | ceph-2:17.2.6-70.el9cp | RHSA-2023:3623 |
Frequently Asked Questions
Is CVE-2021-4231 in your dependencies?
Find it across npm, including transitive dependencies.