CVE-2021-27436Network attack vector

Session hijacking via user-triggered cross-site scripting

Published Mar 18, 2021 · Updated Aug 3, 2024

Cross-site scripting in Advantech WebAccess/SCADA 9.0 and earlier allows remote attackers to execute JavaScript in a user's browser. Advantech and CISA have not disclosed the affected page or parameter, only that crafted JavaScript is sent to an unsuspecting user. User interaction is required; successful execution can steal session cookies, redirect the browser, or perform unintended browser actions.

CVSS severity6.1
Medium
EPSS probability0.69%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Cross-site scripting in Advantech WebAccess/SCADA 9.0 and earlier allows remote attackers to execute JavaScript in a user's browser. Advantech and CISA have not disclosed the affected page or parameter, only that crafted JavaScript is sent to an unsuspecting user. User interaction is required; successful execution can steal session cookies, redirect the browser, or perform unintended browser actions.

The record

CVE
CVE-2021-27436
Published
Mar 18, 2021
Updated
Aug 3, 2024
Vendor
Advantech
Product
WebAccess/SCADA
Classifications
CWE-79, T1539
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 18, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record 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=Versions 9.0 and prior

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Advantech · WebAccess/SCADAversion=Versions 9.0 and prior

Published CVSS scores

6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/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

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1539Steal Web Session Cookie

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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo