How severe is CVE-2021-29459?

CVE-2021-29459 has a CVSS score of 6.1/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2021-29459?

CVE-2021-29459 affects the following packages: org.xwiki.platform:xwiki-platform-oldcore (Maven), org.xwiki.platform:xwiki-platform-oldcore (Maven), org.xwiki.platform:xwiki-platform-web (Maven), org.xwiki.platform:xwiki-platform-web (Maven). Ecosystems affected: Maven.

How do I fix CVE-2021-29459?

Update org.xwiki.platform:xwiki-platform-oldcore to 12.6.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-29459 is resolved across your whole dependency graph.

How do I detect CVE-2021-29459 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.xwiki.platform:xwiki-platform-oldcore, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2021-29459 if there is no patch (or I can't update yet)?

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.

Is CVE-2021-29459 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2021-29459, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-29459?

CVE-2021-29459 has an EPSS (Exploit Prediction Scoring System) score of 1.1%, placing it in the 65th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2021-29459?

CVE-2021-29459 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2021-29459 published, and has it been updated?

CVE-2021-29459 was published on April 20, 2021 and was last updated on August 7, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕

☕ Maven

Not in CISA KEV

MEDIUM severity

CVE-2021-29459 — xwiki-platform-oldcore

MEDIUM

CVE-2021-29459 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in org.xwiki.platform:xwiki-platform-oldcore. 1 public exploit reference exists, so weaponization risk is real. A fix is available for org.xwiki.platform:xwiki-platform-oldcore — see the affected versions and patch details below.

XSS Cross Site Scripting

Also known asGHSA-5c66-v29h-xjh8

Published

Apr 20, 2021

Updated

Aug 7, 2026

Affected

4 pkgs

Patched

4 / 4

Exploits

1 known

Exploitation data as of Oct 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.1%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs65th percentile — riskier than 65% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2021-29459 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,987 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

4 pkgs affected

☕org.xwiki.platform:xwiki-platform-oldcore☕org.xwiki.platform:xwiki-platform-oldcore☕org.xwiki.platform:xwiki-platform-web☕org.xwiki.platform:xwiki-platform-web

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

Impact

It is possible to persistently inject scripts in XWiki.

For unregistred users:

By filling simple text fields

For registered users:

By filling their personal information
(if they have edit rights) By filling the values of static lists using App Within Minutes

That can lead to user's session hijacking, and if used in conjunction with a social engineering attack it can also lead to disclosure of sensitive data, CSRF attacks and other security vulnerabilities. That can also lead to the attacker taking over an account. If the victim has administrative rights it might even lead to code execution on the server, depending on the application and the privileges of the account.

Patches

It has been patched on XWiki 12.8 and 12.6.3.

Workarounds

There is no easy workaround except upgrading XWiki.

References

https://jira.xwiki.org/browse/XWIKI-17374

For more information

If you have any questions or comments about this advisory:

Open an issue in Jira XWiki
Email us at our security mailing list

Affected Packages

4 total 4 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.xwiki.platform:xwiki-platform-oldcore`	all versions	12.6.3`org.xwiki.platform:xwiki-platform-oldcore:12.6.3`
☕Maven	`org.xwiki.platform:xwiki-platform-oldcore`	≥ 12.6.4&&< 12.8	12.8`org.xwiki.platform:xwiki-platform-oldcore:12.8`
☕Maven	`org.xwiki.platform:xwiki-platform-web`	all versions	12.6.3`org.xwiki.platform:xwiki-platform-web:12.6.3`
☕Maven	`org.xwiki.platform:xwiki-platform-web`	≥ 12.6.4&&< 12.8	12.8`org.xwiki.platform:xwiki-platform-web:12.8`

Affected Products

1 product · 2 configurations

Application

xwikixwiki

≥ 12.6.4 && < 12.8

range

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

XWiki Platform is a generic wiki platform offering runtime services for …

github.comNVDApr 2021

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.xwiki.platform:xwiki-platform-oldcore, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.xwiki.platform:xwiki-platform-oldcore to 12.6.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-29459 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.

Frequently Asked Questions

### Impact It is possible to persistently inject scripts in XWiki. For unregistred users: - By filling simple text fields For registered users: - By filling their personal information - (if they have edit rights) By filling the values of static lists using App Within Minutes That can lead to user's session hijacking, and if used in conjunction with a social engineering attack it can also lead to disclosure of sensitive data, CSRF attacks and other security vulnerabilities. That can also lead to the attacker taking over an account. If the victim has administrative rights it might even lead t

O3 Security · Impact-Aware SCA

Is CVE-2021-29459 in your dependencies?

Find it across Maven, including transitive dependencies.

Scan my dependencies How O3 SCA works

CVSS Score

6.1/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CWE Classification

CWE-79Cross-site Scripting (XSS)

Weaponization

No known public exploit tooling found.

OpenSSF Scorecard

Package health score

xwiki-platform

5.6/10

Code-Review5/10

Maintained10/10

Branch-ProtectionN/A

Assessed Oct 5, 2026

Timeline

Disclosed

Apr 20, 2021

First exploit

Apr 29, 2021

Last updated

Aug 7, 2026

Identifiers

CVE-2021-29459

GHSA-5c66-v29h-xjh8

References

Advisorynvd.nist.gov Evidencegithub.com

Related vulnerabilities

This CVE is medium severity; 8 of 8 other CVEs affecting xwiki-platform-oldcore are rated as high or higher (top: critical).

CVE-2026-34151CVE-2026-40104CVE-2026-33229CVE-2025-54125CVE-2025-54124CVE-2025-54385CVE-2025-49586CVE-2024-56158

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedAug 7, 2026

CVE-2021-29459 — xwiki-platform-oldcore

EPSS Exploitation Probability

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

Description

Impact

Patches

Workarounds

References

For more information

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Frequently Asked Questions

Is CVE-2021-29459 in your dependencies?