CVE-2026-21966Network attack vector

Reflected XSS via unsanitized query parameter names

Published Jan 20, 2026 · Updated Jan 20, 2026

Reflected XSS in Oracle Hospitality OPERA 5 Property Services allows remote attackers to execute JavaScript through a crafted HTTP request. The OperaPrint servlet embeds a reused query string in an onload attribute, while sanitizeParameterString filters only parameter values; an ' entity in a parameter name escapes the quoted context. Builds 5.6.19.23, 5.6.25.17, 5.6.26.10, and 5.6.27.4 require a victim to follow the crafted URL, exposing the browser session to unauthorized data access and actions.

CVSS severity6.1
Medium
EPSS probability0.18%
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 Oracle Hospitality OPERA 5 Property Services allows remote attackers to execute JavaScript through a crafted HTTP request. The OperaPrint servlet embeds a reused query string in an onload attribute, while sanitizeParameterString filters only parameter values; an ' entity in a parameter name escapes the quoted context. Builds 5.6.19.23, 5.6.25.17, 5.6.26.10, and 5.6.27.4 require a victim to follow the crafted URL, exposing the browser session to unauthorized data access and actions.

The record

CVE
CVE-2026-21966
Published
Jan 20, 2026
Updated
Jan 20, 2026
Vendor
Oracle Corporation
Product
Oracle Hospitality OPERA Property Management
Classifications
T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 20, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 20, 2026Record 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=5.6.19.23
  2. Affected versionversion=5.6.25.17
  3. Affected versionversion=5.6.26.10
  4. Affected versionversion=5.6.27.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Oracle Corporation · Oracle Hospitality OPERA Property Managementversion=5.6.19.23; version=5.6.25.17; version=5.6.26.10; version=5.6.27.4

Published CVSS scores

5.1PwC Hong Kong Dark LabCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
6.1Oracle CorporationCVSS:3.1/AV:N/AC:L/PR:N/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

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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