How severe is CVE-2021-29438?

CVE-2021-29438 has a CVSS score of 5.4/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2021-29438?

CVE-2021-29438 affects the following packages: @nextcloud/dialogs (npm). Ecosystems affected: npm.

How do I fix CVE-2021-29438?

Update @nextcloud/dialogs to 3.1.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-29438 is resolved across your whole dependency graph.

How do I detect CVE-2021-29438 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @nextcloud/dialogs, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2021-29438 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-2021-29438 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-29438 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2021-29438?

CVE-2021-29438 has an EPSS (Exploit Prediction Scoring System) score of 0.7%, placing it in the 52th 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-2021-29438?

CVE-2021-29438 is classified as Cross-site Scripting (XSS) (CWE-79), CWE-80 (CWE-80). These weakness types 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-2021-29438 published, and has it been updated?

CVE-2021-29438 was published on April 13, 2021 and was last updated on August 27, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦

📦 npm

Not in CISA KEV

MEDIUM severity

CVE-2021-29438 — @nextcloud/dialogs

MEDIUM

CVE-2021-29438 is a medium-severity (CVSS 5.4) Cross-site Scripting (XSS) vulnerability in @nextcloud/dialogs. A fix is available for @nextcloud/dialogs — see the affected versions and patch details below.

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

Also known asGHSA-g3fq-3v3g-mh32

Published

Apr 13, 2021

Updated

Aug 27, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 11, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

0.7%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs52th percentile — riskier than 52% of all scored CVEsHighest risk

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

How urgent is this, really

CVE-2021-29438 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

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.

10other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

@nextcloud/dialogsnpm

60Kdownloads / week

Description

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.

Patches

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.

Workarounds

Make sure no user-supplied input flows into toasts.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`@nextcloud/dialogs`	all versions	3.1.2`npm install @nextcloud/dialogs@3.1.2`

Affected Products

1 product · 1 configurations

Application

nextcloud\/dialogsnextcloud\/dialogs_project

< 3.1.2

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @nextcloud/dialogs, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @nextcloud/dialogs to 3.1.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-29438 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 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. ### Patches 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. ### Workarounds Make sure no user-supplied input flows into toasts.

O3 Security · Impact-Aware SCA

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CVSS Score

5.4/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Raw vector

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

CWE Classification

CWE-79Cross-site Scripting (XSS)CWE-80CWE-80

Weaponization

No known public exploit tooling found.

OpenSSF Scorecard

Package health score

nextcloud-dialogs

7.3/10

Maintained10/10

Code-Review10/10

Branch-Protection4/10

Assessed Oct 5, 2026

Timeline

Disclosed

Apr 13, 2021

Last updated

Aug 27, 2026

Identifiers

CVE-2021-29438

GHSA-g3fq-3v3g-mh32

References

Advisorygithub.com Advisorynvd.nist.gov Webnpmjs.com Webnpmjs.com

Related vulnerabilities

This CVE is medium severity; 8 of 8 other CVEs with CWE-79 are rated as high or higher (top: high).

CVE-2026-91127CVE-2026-77606CVE-2026-84992CVE-2026-77608CVE-2026-77607GHSA-9rcc-pmj8-ffhrCVE-2026-77616CVE-2025-61682Browse all CWE-79

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedAug 27, 2026

CVE-2021-29438 — @nextcloud/dialogs

EPSS Exploitation Probability

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

Description

Impact

Patches

Workarounds

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Frequently Asked Questions

Is CVE-2021-29438 in your dependencies?