CVE-2019-15618Network attack vector

Admin-browser script execution via unescaped updater data

Published Feb 4, 2020 · Updated Aug 5, 2024

Reflected XSS in Nextcloud Server before 14.0.9 and 15.0.0 through 15.0.5 allows remote attackers to run script in an administrator's browser. The Updater's checkForUpdate path builds an HTML status message from update-server response values without escaping them, reflecting crafted markup into the web interface. Exploitation requires administrative access and an administrator who starts the web Updater from a malicious location; the injected script executes in that browser's Nextcloud origin.

CVSS severity4.8
Medium
EPSS probability0.73%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reflected XSS in Nextcloud Server before 14.0.9 and 15.0.0 through 15.0.5 allows remote attackers to run script in an administrator's browser. The Updater's checkForUpdate path builds an HTML status message from update-server response values without escaping them, reflecting crafted markup into the web interface. Exploitation requires administrative access and an administrator who starts the web Updater from a malicious location; the injected script executes in that browser's Nextcloud origin.

The record

CVE
CVE-2019-15618
Published
Feb 4, 2020
Updated
Aug 5, 2024
Vendor
Nextcloud GmbH
Product
Nextcloud Server
Classifications
CWE-79, T1203
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Feb 4, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=15.0.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Nextcloud GmbH · Nextcloud Serverversion=15.0.6

Published CVSS scores

3.5NIST NVDAV:N/AC:M/Au:S/C:N/I:P/A:N
4.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N

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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

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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