CVE-2026-120421
Reflected XSS via client window id in URL client window mode
Description
In Eclipse Mojarra versions 2.2.0 through 4.0.28, 4.1.0 through 4.1.19, and 5.0.0-M1 through 5.0.0-M11, when URL client window mode is enabled (`jakarta.faces.CLIENT_WINDOW_MODE=url`), the client window id from the `jfwid` or `jakarta.faces.ClientWindow` request parameter is appended to generated URLs without URL-encoding. `h:button` renders such a URL into a JavaScript string literal, which allows reflected cross-site scripting. With `com.sun.faces.enableCspNonce=true`, the injected script runs on page load inside the nonce script element, bypassing the Content Security Policy.
INFO
Published Date :
Nov. 4, 2026, 3:17 p.m.
Last Modified :
Nov. 4, 2026, 3:17 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | e51fbebd-6053-4e49-959f-1b94eeb69a2c | ||||
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update Eclipse Mojarra to a version that includes the fix.
- Ensure client window mode is disabled if not required.
- Validate that URL parameters are properly encoded.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-120421.
| URL | Resource |
|---|---|
| https://gitlab.eclipse.org/security/cve-assignment/-/work_items/536 | |
| https://gitlab.eclipse.org/security/vulnerability-reports/-/work_items/1332 |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-120421 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-120421
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-120421 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-120421 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by [email protected]
Nov. 04, 2026
Action Type Old Value New Value Added Description In Eclipse Mojarra versions 2.2.0 through 4.0.28, 4.1.0 through 4.1.19, and 5.0.0-M1 through 5.0.0-M11, when URL client window mode is enabled (`jakarta.faces.CLIENT_WINDOW_MODE=url`), the client window id from the `jfwid` or `jakarta.faces.ClientWindow` request parameter is appended to generated URLs without URL-encoding. `h:button` renders such a URL into a JavaScript string literal, which allows reflected cross-site scripting. With `com.sun.faces.enableCspNonce=true`, the injected script runs on page load inside the nonce script element, bypassing the Content Security Policy. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Added CWE CWE-79 Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/120xxx/CVE-2026-120421.json">CVE-2026-120421</a> Added Reference https://gitlab.eclipse.org/security/cve-assignment/-/work_items/536 Added Reference https://gitlab.eclipse.org/security/vulnerability-reports/-/work_items/1332