What is CVE-2021-29438?

CVE-2021-29438 is a medium-severity cross-site scripting (XSS) vulnerability in @nextcloud/dialogs (npm), affecting versions < 3.1.2. It is fixed in 3.1.2. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.

How severe is CVE-2021-29438?

CVE-2021-29438 has a CVSS score of 4.6 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Which versions of @nextcloud/dialogs are affected by CVE-2021-29438?

@nextcloud/dialogs (npm) versions < 3.1.2 is affected.

Is there a fix for CVE-2021-29438?

Yes. CVE-2021-29438 is fixed in 3.1.2. Upgrade to this version or later.

Is CVE-2021-29438 exploitable, and should I be worried?

Whether CVE-2021-29438 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

What actually determines whether CVE-2021-29438 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

How do I fix CVE-2021-29438?

Upgrade @nextcloud/dialogs to 3.1.2 or later.

CVE-2021-29438 in @nextcloud/dialogs

Q: How severe is CVE-2021-29438?

CVE-2021-29438 has a CVSS score of 4.6 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Q: Which versions of @nextcloud/dialogs are affected by CVE-2021-29438?

@nextcloud/dialogs (npm) versions < 3.1.2 is affected.

Q: Is there a fix for CVE-2021-29438?

Yes. CVE-2021-29438 is fixed in 3.1.2. Upgrade to this version or later.

Q: Is CVE-2021-29438 exploitable, and should I be worried?

Whether CVE-2021-29438 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

Q: What actually determines whether CVE-2021-29438 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

Q: How do I fix CVE-2021-29438?

Upgrade @nextcloud/dialogs to 3.1.2 or later.

Summary

Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS) in @nextcloud/dialogs

Workarounds

Make sure no user-supplied input flows into toasts.

Impact

The Nextcloud dialogs library before 3.1.2 did insufficiently escape text input passed to a toast. If your application displays toasts with user-supplied input, this could lead to a XSS vulnerability.

Note: Nextcloud Server employs a strict Content Security Policy that mitigates the risk of these XSS vulnerabilities.

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

CVE-2021-29438 has a CVSS score of 4.6 (Medium). The vector is network-reachable, low privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.1.2); upgrading removes the vulnerable code path.

Affected versions

@nextcloud/dialogs (< 3.1.2)

Security releases

@nextcloud/dialogs → 3.1.2 (npm)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

Already deployed Kodem?

See it in your environment New to Kodem? Get a demo →

Remediation advice

The vulnerability has been patched in version 3.1.2. If you need to display HTML in the toast, explicitly pass the options.isHTML config flag.

Frequently Asked Questions

What is CVE-2021-29438? CVE-2021-29438 is a medium-severity cross-site scripting (XSS) vulnerability in @nextcloud/dialogs (npm), affecting versions < 3.1.2. It is fixed in 3.1.2. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
How severe is CVE-2021-29438? CVE-2021-29438 has a CVSS score of 4.6 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
Which versions of @nextcloud/dialogs are affected by CVE-2021-29438? @nextcloud/dialogs (npm) versions < 3.1.2 is affected.
Is there a fix for CVE-2021-29438? Yes. CVE-2021-29438 is fixed in 3.1.2. Upgrade to this version or later.
Is CVE-2021-29438 exploitable, and should I be worried? Whether CVE-2021-29438 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
What actually determines whether CVE-2021-29438 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
How do I fix CVE-2021-29438? Upgrade @nextcloud/dialogs to 3.1.2 or later.