CVE-2021-25668Network attack vector

Remote code execution via malformed webserver POST request

Published Apr 22, 2021 · Updated Aug 3, 2024

Heap-based buffer overflow in Siemens SCALANCE X-200 webservers before 5.5.1 or 5.2.5 allows remote attackers to execute code. The embedded webserver incorrectly processes crafted POST requests and writes beyond a heap allocation. No authentication or user interaction is required; exploitation can crash the switch or execute code with device-wide consequences.

CVSS severity9.8
Critical
EPSS probability1.57%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-based buffer overflow in Siemens SCALANCE X-200 webservers before 5.5.1 or 5.2.5 allows remote attackers to execute code. The embedded webserver incorrectly processes crafted POST requests and writes beyond a heap allocation. No authentication or user interaction is required; exploitation can crash the switch or execute code with device-wide consequences.

The record

CVE
CVE-2021-25668
Published
Apr 22, 2021
Updated
Aug 3, 2024
Vendor
Siemens
Product
SCALANCE X212-2LD
Classifications
CWE-122, T0819
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

9.8INCIBE-CERTCVSS: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 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-122Heap-based Buffer Overflow
T0819Exploit 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

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Your stack

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