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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2021-29438: 0.70% estimated exploitation activity in the next 30 days; percentile 53.33 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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.

Published by the source

16 Apr 2021, 19:52 UTC

Last modified by the source

8 Jul 2026, 06:28 UTC

Source last checked

26 Oct 2026, 12:20 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-g3fq-3v3g-mh32

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-g3fq-3v3g-mh32

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# Patch Next advisory brief: CVE-2021-29438

Advisory: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS) in @nextcloud/dialogs
IDs: CVE-2021-29438, GHSA-g3fq-3v3g-mh32
Record: https://patchnext.com/advisories/cve-2021-29438 (revision 2, source checked 26 Oct 2026, 12:20 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @nextcloud/dialogs 3.1.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @nextcloud/dialogs: affected < 3.1.2; fixed in 3.1.2

## Suggested inspection (read-only)
- `npm ls @nextcloud/dialogs --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @nextcloud/dialogs.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-g3fq-3v3g-mh32 (OSV record GHSA-g3fq-3v3g-mh32 lists affected ranges: npm @nextcloud/dialogs >=0 <3.1.2 (fixed))
- Verified: https://github.com/advisories/GHSA-g3fq-3v3g-mh32 (GitHub-reviewed advisory GHSA-g3fq-3v3g-mh32 lists affected ranges: npm @nextcloud/dialogs >=0 <3.1.2)

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