CVE-2021-25669Network attack vector

Unauthenticated code execution via POST stack overwrite

Published Apr 22, 2021 · Updated Aug 3, 2024

Stack overflow in Siemens SCALANCE X-200 firmware before 5.2.5 or 5.5.1 allows remote attackers to execute code through HTTP POST requests. The embedded web server incorrectly processes crafted POST data and writes beyond a stack buffer. No authentication or user interaction is required; exploitation can instead crash the device, and Siemens has not disclosed the affected handler or field.

CVSS severity9.8
Critical
EPSS probability2.13%
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

Stack overflow in Siemens SCALANCE X-200 firmware before 5.2.5 or 5.5.1 allows remote attackers to execute code through HTTP POST requests. The embedded web server incorrectly processes crafted POST data and writes beyond a stack buffer. No authentication or user interaction is required; exploitation can instead crash the device, and Siemens has not disclosed the affected handler or field.

The record

CVE
CVE-2021-25669
Published
Apr 22, 2021
Updated
Aug 3, 2024
Vendor
Siemens
Product
SCALANCE X212-2LD
Classifications
CWE-121, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 22, 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=All versions < V5.2.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Siemens · SCALANCE X212-2LDversion=All versions < V5.2.5
Siemens · SCALANCE X202-2P IRTversion=All versions < 5.5.1
Siemens · SCALANCE X204-2FMversion=All versions < V5.2.5
Siemens · SCALANCE XF204-2version=All versions < V5.2.5
Siemens · SCALANCE X204-2TSversion=All versions < V5.2.5
Siemens · SCALANCE X204-2version=All versions < V5.2.5
Siemens · SCALANCE X206-1version=All versions < V5.2.5
Siemens · SCALANCE X204-2LDversion=All versions < V5.2.5
Siemens · SCALANCE XF204IRTversion=All versions < 5.5.1
Siemens · SCALANCE X206-1LDversion=All versions < V5.2.5
Siemens · SCALANCE X204 IRTversion=All versions < 5.5.1
Siemens · SCALANCE X202-2P IRT PROversion=All versions < 5.5.1
Siemens · SCALANCE X204-2LD TSversion=All versions < V5.2.5
Siemens · SCALANCE X216version=All versions < V5.2.5
Siemens · SCALANCE XF202-2P IRTversion=All versions < 5.5.1
Siemens · SCALANCE X202-2 IRTversion=All versions < 5.5.1
Siemens · SCALANCE X208PROversion=All versions < V5.2.5
Siemens · SCALANCE X224version=All versions < V5.2.5
Siemens · SCALANCE X208version=All versions < V5.2.5
Siemens · SCALANCE X201-3P IRT PROversion=All versions < 5.5.1
Siemens · SCALANCE XF201-3P IRTversion=All versions < 5.5.1
Siemens · SCALANCE XF208version=All versions < V5.2.5
Siemens · SCALANCE XF204-2BA IRTversion=All versions < 5.5.1
Siemens · SCALANCE X204 IRT PROversion=All versions < 5.5.1
Siemens · SCALANCE XF204version=All versions < V5.2.5
Siemens · SCALANCE X201-3P IRTversion=All versions < 5.5.1
Siemens · SCALANCE XF206-1version=All versions < V5.2.5
Siemens · SCALANCE X200-4P IRTversion=All versions < 5.5.1
Siemens · SCALANCE X212-2version=All versions < V5.2.5

Published CVSS scores

9.8Siemens ProductCERTCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-121Stack-based Buffer Overflow
T1190Exploit Public-Facing Application

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