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Nextcloud ServerApplication · Nextcloud

CVE-2023-48302

MEDIUM · 5.4 CVSS v3.1 Published 2023-11-21
Fix available
A fix is available. Upgrade to 25.0.13 / 26.0.8 or later.
See remediation →
58/100
Remediation priority · Elevated
Remotely reachable Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Nextcloud Server provides data storage for Nextcloud, an open source cloud platform. Starting in version 25.0.0 and prior to versions 25.0.13, 26.0.8, and 27.1.3 of Nextcloud Server and Nextcloud Enterprise Server, when a user is tricked into copy pasting HTML code without markup (Ctrl+Shift+V) the markup will actually render. Nextcloud Server and Nextcloud Enterprise Server versions 25.0.13, 26.0.8, and 27.1.3 contain a fix for this issue. As a workaround, disable app text.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-79

Untrusted input is placed into a web page without being neutralised, so an attacker's markup or script executes in another user's browser. That can hijack sessions, capture keystrokes, or silently perform actions as the victim. Fixing it properly means context-aware output encoding everywhere data meets HTML, backed by a content-security policy as a second line of defence.

General guidance for the cross-site scripting (xss) class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Nextcloud ServerApplication
Affected:>= 25.0.0, < 25.0.13>= 26.0.0, < 26.0.8>= 27.0.0, < 27.1.3

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

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

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 25.0.13 / 26.0.8 / 27.1.3 or later
Fixed in 25.0.1326.0.827.1.3
Vendor patch github.com →
Recommended fix High confidence

Upgrade to 25.0.13 (for 25.x), 26.0.8 (for 26.x), or 27.1.3 (for 27.x) depending on current major version

  1. Identify the current Nextcloud Server version (check admin settings or occ --version)
  2. Determine the appropriate upgrade target based on current major version: if 25.x upgrade to 25.0.13, if 26.x upgrade to 26.0.8, if 27.x upgrade to 27.1.3
  3. Create a complete backup of the Nextcloud instance including database and data directory
  4. Follow the standard Nextcloud upgrade procedure: disable all third-party apps, stop the web server, replace the server files, run occ upgrade, re-enable apps
  5. Restart the web server and verify the upgrade was successful
  6. As an alternative immediate mitigation, disable the 'text' app by running: occ app:disable text

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $900. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-48302 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data