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Full vulnerability report · 2021
CVE-2021-25668High confidence

Siemens SCALANCE X200-4P IRT — Heap-based Buffer Overflow

Siemens · SCALANCE X200-4P IRT

9.8CriticalCVSS 3.1
Recommended action
Patch only the product branches with a verified fix

Critical technical impact with a remotely reachable, unauthenticated path; no CISA KEV confirmation is currently recorded. Verified remediation exists for at least one product or source, but 29 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityCriticalOperational priority:Critical, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 1.57% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs Siemens SCALANCE X200-4P IRT and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 3 daysRemediation target: Within 90 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Cross-source reconciliation

Remediation availability differs by product scope

Verified remediation exists for at least one product or source, but 29 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
SSA-187092 · CSAF 2.0 · revision 2 · finalSiemens ProductCERTSSA-187092: Several Buffer-Overflow Vulnerabilities in Web Server of SCALANCE X-200
29 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • SCALANCE X200-4P IRT
  • SCALANCE X201-3P IRT
  • SCALANCE X201-3P IRT PRO
  • SCALANCE X202-2 IRT
  • SCALANCE X202-2P IRT (incl. SIPLUS NET variant)
  • SCALANCE X202-2P IRT PRO
  • SCALANCE X204 IRT
  • SCALANCE X204 IRT PRO
  • SCALANCE X204-2 (incl. SIPLUS NET variant)
  • SCALANCE X204-2FM
  • SCALANCE X204-2LD (incl. SIPLUS NET variant)
  • SCALANCE X204-2LD TS
Summary
Incorrect processing of POST requests in the webserver may result in write out of bounds in heap. An attacker might leverage this to cause denial-of-service on the device and potentially remotely execute code.
Remediation
Update to V5.5.1 or later version
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2021-12560

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionPatch only the product branches with a verified fix

Critical technical impact with a remotely reachable, unauthenticated path; no CISA KEV confirmation is currently recorded. Verified remediation exists for at least one product or source, but 29 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
01

What, why and how

A vulnerability has been identified in SCALANCE X200-4P IRT (All versions < 5.5.1), SCALANCE X201-3P IRT (All versions < 5.5.1), SCALANCE X201-3P IRT PRO (All versions < 5.5.1), SCALANCE X202-2 IRT (All versions < 5.5.1), SCALANCE X202-2P IRT (incl. SIPLUS NET variant) (All versions < 5.5.1), SCALANCE X202-2P IRT PRO (All versions < 5.5.1), SCALANCE X204 IRT (All versions < 5.5.1), SCALANCE X204 IRT PRO (All versions < 5.5.1), SCALANCE X204-2 (incl. SIPLUS NET variant) (All versions < V5.2.5), SCALANCE X204-2FM (All versions < V5.2.5), SCALANCE X204-2LD (incl. SIPLUS NET variant) (All versions < V5.2.5), SCALANCE X204-2LD TS (All versions < V5.2.5), SCALANCE X204-2TS (All versions < V5.2.5), SCALANCE X206-1 (All versions < V5.2.5), SCALANCE X206-1LD (All versions < V5.2.5), SCALANCE X208 (incl. SIPLUS NET variant) (All versions < V5.2.5), SCALANCE X208PRO (All versions < V5.2.5), SCALANCE X212-2 (incl. SIPLUS NET variant) (All versions < V5.2.5), SCALANCE X212-2LD (All versions < V5.2.5), SCALANCE X216 (All versions < V5.2.5), SCALANCE X224 (All versions < V5.2.5), SCALANCE XF201-3P IRT (All versions < 5.5.1), SCALANCE XF202-2P IRT (All versions < 5.5.1), SCALANCE XF204 (All versions < V5.2.5), SCALANCE XF204 IRT (All versions < 5.5.1), SCALANCE XF204-2 (incl. SIPLUS NET variant) (All versions < V5.2.5), SCALANCE XF204-2BA IRT (All versions < 5.5.1), SCALANCE XF206-1 (All versions < V5.2.5), SCALANCE XF208 (All versions < V5.2.5). Incorrect processing of POST requests in the webserver may result in write out of bounds in heap. An attacker might leverage this to cause denial-of-service on the device and potentially remotely execute code.

What

A vulnerability has been identified in SCALANCE X200-4P IRT (All versions < 5.5.1), SCALANCE X201-3P IRT (All versions < 5.5.1), SCALANCE X201-3P IRT PRO (All versions < 5.5.1), SCALANCE X202-2 IRT (All versions < 5.5.1), SCALANCE X202-2P IRT (incl. SIPLUS NET variant) (All versions < 5.5.1), SCALANCE X202-2P IRT PRO (All versions < 5.5.1), SCALANCE X204 IRT (All versions < 5.5.1), SCALANCE X204 IRT PRO (All versions < 5.5.1), SCALANCE X204-2 (incl. SIPLUS NET variant) (All versions < V5.2.5), SCALANCE X204-2FM (All versions < V5.2.5), SCALANCE X204-2LD (incl. SIPLUS NET variant) (All versions < V5.2.5), SCALANCE X204-2LD TS (All versions < V5.2.5), SCALANCE X204-2TS (All versions < V5.2.5), SCALANCE X206-1 (All versions < V5.2.5), SCALANCE X206-1LD (All versions < V5.2.5), SCALANCE X208 (incl. SIPLUS NET variant) (All versions < V5.2.5), SCALANCE X208PRO (All versions < V5.2.5), SCALANCE X212-2 (incl. SIPLUS NET variant) (All versions < V5.2.5), SCALANCE X212-2LD (All versions < V5.2.5), SCALANCE X216 (All versions < V5.2.5), SCALANCE X224 (All versions < V5.2.5), SCALANCE XF201-3P IRT (All versions < 5.5.1), SCALANCE XF202-2P IRT (All versions < 5.5.1), SCALANCE XF204 (All versions < V5.2.5), SCALANCE XF204 IRT (All versions < 5.5.1), SCALANCE XF204-2 (incl. SIPLUS NET variant) (All versions < V5.2.5), SCALANCE XF204-2BA IRT (All versions < 5.5.1), SCALANCE XF206-1 (All versions < V5.2.5), SCALANCE XF208 (All versions < V5.2.5). Incorrect processing of POST requests in the webserver may result in write out of bounds in heap. An attacker might leverage this to cause denial-of-service on the device and potentially remotely execute code.

Why

A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may execute code or commands in the affected security context.

What

A vulnerability has been identified in SCALANCE X200-4P IRT (All versions < 5.5.1), SCALANCE X201-3P IRT (All versions < 5.5.1), SCALANCE X201-3P IRT PRO (All versions < 5.5.1), SCALANCE X202-2 IRT (All versions < 5.5.1), SCALANCE X202-2P IRT (incl. SIPLUS NET variant) (All versions < 5.5.1), SCALANCE X202-2P IRT PRO (All versions < 5.5.1), SCALANCE X204 IRT (All versions < 5.5.1), SCALANCE X204 IRT PRO (All versions < 5.5.1), SCALANCE X204-2 (incl. SIPLUS NET variant) (All versions < V5.2.5), SCALANCE X204-2FM (All versions < V5.2.5), SCALANCE X204-2LD (incl. SIPLUS NET variant) (All versions < V5.2.5), SCALANCE X204-2LD TS (All versions < V5.2.5), SCALANCE X204-2TS (All versions < V5.2.5), SCALANCE X206-1 (All versions < V5.2.5), SCALANCE X206-1LD (All versions < V5.2.5), SCALANCE X208 (incl. SIPLUS NET variant) (All versions < V5.2.5), SCALANCE X208PRO (All versions < V5.2.5), SCALANCE X212-2 (incl. SIPLUS NET variant) (All versions < V5.2.5), SCALANCE X212-2LD (All versions < V5.2.5), SCALANCE X216 (All versions < V5.2.5), SCALANCE X224 (All versions < V5.2.5), SCALANCE XF201-3P IRT (All versions < 5.5.1), SCALANCE XF202-2P IRT (All versions < 5.5.1), SCALANCE XF204 (All versions < V5.2.5), SCALANCE XF204 IRT (All versions < 5.5.1), SCALANCE XF204-2 (incl. SIPLUS NET variant) (All versions < V5.2.5), SCALANCE XF204-2BA IRT (All versions < 5.5.1), SCALANCE XF206-1 (All versions < V5.2.5), SCALANCE XF208 (All versions < V5.2.5). Incorrect processing of POST requests in the webserver may result in write out of bounds in heap. An attacker might leverage this to cause denial-of-service on the device and potentially remotely execute code.

Why

A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may execute code or commands in the affected security context.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Heap-based Buffer Overflow → execute code or commands in the affected security context
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-122 ↗

CWE-122: Heap-based Buffer Overflow. A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
After compromise, an attacker may use built-in shells, scripting engines, scheduled tasks and native network utilities for discovery, persistence or movement. This is a plausible LoTL path, not evidence that it has occurred for every attack.
NetworkUnauthenticatedRemote code executionCWE-122
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

Cyber Security Agency of Singapore · English · CSA-SB-20210428Security Bulletin 28 Apr 2021

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 28 Apr 2021, published on 28 April 2021. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-256Multiples vulnérabilités dans les produits Siemens SCALANCE

De multiples vulnérabilités ont été découvertes dans les produits Siemens SCALANCE. Elles permettent à un attaquant de provoquer une exécution de code arbitraire à distance et un contournement de la politique de sécurité.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2021-006154複数のシーメンス製品における境界外書き込みに関する脆弱性

複数のシーメンス製品には、境界外書き込みに関する脆弱性が存在します。

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Fix availability varies by product
Affected
Fixed
Update to V5.5.1 or later version
Action
Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 22 Apr 2021 · Last source change 3 Aug 2024, 20:11 UTC · CWE-122 · Heap-based Buffer Overflow

CVE recordCVE.org · 5.1
CVSS sourceNIST NVD
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2021-12560
Product sourceVendor CSAF · Siemens ProductCERT
Remediation sourceVendor CSAF · Siemens ProductCERT
CWE sourceCNA
NVD statusNVD modified after enrichment

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Affected versionsThe structured affected or fixed version information changed.
    Before
    All versions < 5.5.1 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    After
    All versions < 5.5.1 · Fixed: Update to V5.5.1 or later version
    Siemens ProductCERT ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
Fixed release recorded from official guidance
ENISA EUVD · EUVD-2021-12560↗CVE authority or vendor reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2021-25668 · cve.blacktree.nl