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Full vulnerability report · 2021
CVE-2021-33737High confidence

A vulnerability has been identified in SIMATIC CP 343-1 (incl

Siemens · SIMATIC CP 343-1 (incl. SIPLUS variants)

7.5HighCVSS 3.1
Recommended action
Within 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
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-549234 · CSAF 2.0 · revision 4 · interimSiemens ProductCERTSSA-549234: Denial-of-Service Vulnerability in SIMATIC NET CP Modules
9 known affected

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

  • SIMATIC CP 343-1 (incl. SIPLUS variants)
  • SIMATIC CP 343-1 Advanced (incl. SIPLUS variants)
  • SIMATIC CP 343-1 ERPC (6GK7343-1FX00-0XE0)
  • SIMATIC CP 343-1 Lean (incl. SIPLUS variants)
  • SIMATIC CP 443-1 (6GK7443-1EX30-0XE0)
  • SIMATIC CP 443-1 (6GK7443-1EX30-0XE1)
  • SIMATIC CP 443-1 Advanced (6GK7443-1GX30-0XE0)
  • SIPLUS NET CP 443-1 (6AG1443-1EX30-4XE0)
  • SIPLUS NET CP 443-1 Advanced (6AG1443-1GX30-4XE0)
Summary
Sending a specially crafted packet to port 102/tcp of an affected device could cause a denial of service condition. A restart is needed to restore normal operations.
Remediation
Update to V3.3 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.

Select the national-authority views to include. The exact source language is shown on each matched advisory. Your choice is remembered on this device and encoded in the shareable URL.

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-2021-20414

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 actionWithin 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

A vulnerability has been identified in SIMATIC CP 343-1 (incl. SIPLUS variants) (All versions), SIMATIC CP 343-1 Advanced (incl. SIPLUS variants) (All versions), SIMATIC CP 343-1 ERPC (All versions), SIMATIC CP 343-1 Lean (incl. SIPLUS variants) (All versions), SIMATIC CP 443-1 (All versions < V3.3), SIMATIC CP 443-1 (All versions < V3.3), SIMATIC CP 443-1 Advanced (All versions < V3.3), SIPLUS NET CP 443-1 (All versions < V3.3), SIPLUS NET CP 443-1 Advanced (All versions < V3.3). Sending a specially crafted packet to port 102/tcp of an affected device could cause a denial of service condition. A restart is needed to restore normal operations.

What

A vulnerability has been identified in SIMATIC CP 343-1 (incl. SIPLUS variants) (All versions), SIMATIC CP 343-1 Advanced (incl. SIPLUS variants) (All versions), SIMATIC CP 343-1 ERPC (All versions), SIMATIC CP 343-1 Lean (incl. SIPLUS variants) (All versions), SIMATIC CP 443-1 (All versions < V3.3), SIMATIC CP 443-1 (All versions < V3.3), SIMATIC CP 443-1 Advanced (All versions < V3.3), SIPLUS NET CP 443-1 (All versions < V3.3), SIPLUS NET CP 443-1 Advanced (All versions < V3.3). Sending a specially crafted packet to port 102/tcp of an affected device could cause a denial of service condition. A restart is needed to restore normal operations.

Why

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

What

A vulnerability has been identified in SIMATIC CP 343-1 (incl. SIPLUS variants) (All versions), SIMATIC CP 343-1 Advanced (incl. SIPLUS variants) (All versions), SIMATIC CP 343-1 ERPC (All versions), SIMATIC CP 343-1 Lean (incl. SIPLUS variants) (All versions), SIMATIC CP 443-1 (All versions < V3.3), SIMATIC CP 443-1 (All versions < V3.3), SIMATIC CP 443-1 Advanced (All versions < V3.3), SIPLUS NET CP 443-1 (All versions < V3.3), SIPLUS NET CP 443-1 Advanced (All versions < V3.3). Sending a specially crafted packet to port 102/tcp of an affected device could cause a denial of service condition. A restart is needed to restore normal operations.

Why

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

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 → Improper Restriction of Operations within the Bounds of a Memory Buffer → disrupt the affected service
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-119 ↗

CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer. The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.

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:N/I:N/A:H/E:P/RL:U/RC:C

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.CNoneConfidentiality impact: No direct loss is represented by this metric.INoneIntegrity impact: No direct loss is represented by this metric.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticatedDenial of serviceCWE-119
A

Official authority intelligence

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

CERT-FR · French · CERTFR-2021-AVI-706Multiples vulnérabilités dans les produits Siemens

ord?id=CVE-2020-36475 Référence CVE CVE-2020-36478 https://www.cve.org/CVERecord?id=CVE-2020-36478 Référence CVE CVE-2020-7461 https://www.cve.org/CVERecord?id=CVE-2020-7461 Référence CVE CVE-2021-25665 https://www.cve.org/CVERecord?id=CVE-2021-25665 Référence CVE CVE-2021-27391 https://www.cve.org/CVERecord?id=CVE-2021-27391 Référence CVE CVE-2021-31891 https://www.cve.org/CVERecord?id=CVE-2021-31891 Référence CVE CVE-2021-33716 https://www.cve.org/CVERecord?id=CVE-2021-33716 Référence CVE CVE-2021-33719 https://www.cve.org/CVERecord?id=CVE-2021-33719 Référence CVE CVE-2021-33720 https://www.cve.org/CVERecord?id=CVE-2021-33720 Référence CVE CVE-2021-33737 https://www.cve.org/CVERecord?id=CVE-2021-33737 Référence CVE CVE-2021-37173 https://www.cve.org/CVERecord?id=CVE-2021-37173 Référence CVE CVE-2021-37174 https://www.cve.org/CVERecord?id=CVE-2021-37174 Référence CVE CVE-2021-37175 https://www.cve.org/CVERecord?id=CVE-2021-37175 Référence CVE CVE-2021-37176 https://www.cve.org/CVERecord?id=CVE-2021-37176 Référence CVE CVE-2021-37177 https://www.cve.org/CVERecord?id=CVE-2021-37177 Référence CVE CVE-2021-37181 https://www.cve.org/CVERecord?id=CVE-2021-37181 Référence CVE CVE-2021-37183 https://www.cve.org/CVERecord?id=CVE-2021-37183 Référence CVE CVE-2021-37184 https://www.cve.org/CVERecord?id=

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.
Patch available
Affected
SIMATIC CP 343-1 (incl. SIPLUS variants); SIMATIC CP 343-1 Advanced (incl. SIPLUS variants); SIMATIC CP 343-1 ERPC (6GK7343-1FX00-0XE0); SIMATIC CP 343-1 Lean (incl. SIPLUS variants); SIMATIC CP 443-1 (6GK7443-1EX30-0XE0); SIMATIC CP 443-1 (6GK7443-1EX30-0XE1); SIMATIC CP 443-1 Advanced (6GK7443-1GX30-0XE0); SIPLUS NET CP 443-1 (6AG1443-1EX30-4XE0); SIPLUS NET CP 443-1 Advanced (6AG1443-1GX30-4XE0)
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.
Action
Update to V3.3 or later version
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 14 Sept 2021 · Last source change 3 Aug 2024, 23:58 UTC · CWE-119 · Improper Restriction of Operations within the Bounds of a Memory Buffer

CVE recordCVE.org · 5.1
CVSS sourceCNA
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-2021-20414
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 →

No material field changes have been recorded since change tracking began. Routine source refreshes and cosmetic edits are intentionally excluded.

Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2021-20414↗Vendor CSAF · Siemens ProductCERT↗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-2021-33737 · cve.blacktree.nl