CVE-2025-59788Public exploitNetwork attack vector

Authenticated session compromise via exposed PDF.js viewer

Published Dec 4, 2025 · Updated Dec 11, 2025

Cross-site scripting in Nextcloud Server allows remote authenticated users to access a logged-in victim's files via a crafted PDF link. The files_pdfviewer app exposes PDF.js's unused web/viewer.html example on the Nextcloud origin, where it renders a malicious uploaded PDF and runs embedded JavaScript. Exploitation requires a regular account able to upload and publicly share the PDF, plus a logged-in victim who opens the prepared link; the script acts with that victim's Nextcloud identity.

CVSS severity5.5
Medium
EPSS probability0.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in Nextcloud Server allows remote authenticated users to access a logged-in victim's files via a crafted PDF link. The files_pdfviewer app exposes PDF.js's unused web/viewer.html example on the Nextcloud origin, where it renders a malicious uploaded PDF and runs embedded JavaScript. Exploitation requires a regular account able to upload and publicly share the PDF, plus a logged-in victim who opens the prepared link; the script acts with that victim's Nextcloud identity.

The record

CVE
CVE-2025-59788
Published
Dec 4, 2025
Updated
Dec 11, 2025
Vendor
Nextcloud GmbH
Product
Nextcloud Server
Classifications
CWE-79, T1204.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Dec 4, 2025CVE publishedPublication date reported by the CVE source.
  2. Dec 11, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <22.2.10.33
  2. Affected versionversion=23 <23.0.12.29
  3. Affected versionversion=24 <24.0.12.28
  4. Affected versionversion=25 <25.0.13.23
  5. Affected versionversion=26 <26.0.13.20
  6. Affected versionversion=27 <27.1.11.20
  7. Affected versionversion=28 <28.0.14.11
  8. Affected versionversion=29 <29.0.16.8
  9. Affected versionversion=30 <30.0.17
  10. Affected versionversion=31 <31.0.10
  11. Affected versionversion=32 <32.0.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Nextcloud GmbH · Nextcloud Serverversion=0 <22.2.10.33; version=23 <23.0.12.29; version=24 <24.0.12.28; version=25 <25.0.13.23; version=26 <26.0.13.20; version=27 <27.1.11.20; version=28 <28.0.14.11; version=29 <29.0.16.8; version=30 <30.0.17; version=31 <31.0.10; version=32 <32.0.1

Published CVSS scores

6.4CVE ProgramCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
5.5NextcloudCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1204.001Malicious Link

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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