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CVE-2021-37204

25
FAUCET Score

CVE-2021-37204 describes a denial-of-service vulnerability affecting numerous Siemens SIMATIC controllers and related products, including S7-1200, S7-1500, and ET 200SP Open Controllers. An unauthenticated attacker can exploit this by sending specially crafted packets to port 102/tcp, causing the PLC to crash and requiring a manual restart to restore functionality. This vulnerability carries a CVSSv3.1 score of 7.5 (High) due to its network-based attack vector, low attack complexity, and high impact on availability. While there is no known active exploitation or public exploit code (Metasploit, Nuclei, ExploitDB), the vulnerability has garnered some community discussion and media coverage, indicating awareness within the cybersecurity landscape.

Impacted Technologies

VendorProductVersion(s)CPE
< 2.9.4CPE matchmatch criteria
cpe:2.3:o:siemens:simatic_drive_controller_cpu_1504d_tf_firmware:*:*:*:*:*:*:*:*
< 2.9.4CPE matchmatch criteria
cpe:2.3:o:siemens:simatic_drive_controller_cpu_1507d_tf_firmware:*:*:*:*:*:*:*:*
All Versions ImpactedCPE matchmatch criteria
cpe:2.3:o:siemens:simatic_et_200sp_open_controller_cpu_1515sp_pc2_firmware:*:*:*:*:*:*:*:*
< 4.0CPE matchmatch criteria
cpe:2.3:o:siemens:simatic_s7-plcsim_advanced_firmware:*:*:*:*:*:*:*:*
4.0CPE matchmatch criteria
cpe:2.3:o:siemens:simatic_s7-plcsim_advanced_firmware:4.0:-:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
2.18%
Probability of exploitation in next 30 days
EPSS Percentile
80.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0218 is in the 65th percentile among its peer group of 51,551 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

cert-portal.siemens.com / productcert/pdf/ssa-838121.pdf
PatchVendor Advisory