Siemens Clears Integer Overflow Issues

Sep 16, 2025 | OT Advisories

Siemens has an update and mitigations available to handle integer overflow or wraparound vulnerabilities in its SIMATIC NET CP, SINEMA and SCALANCE, according to a report with CISA.

Successful exploitation of these remotely exploitable vulnerabilities, which Siemens ProductCERT discovered, could allow an attacker to cause a denial-of-service (DoS) condition in the affected devices by exploiting integer overflow bugs.

In one issue, the gmp plugin in strongSwan before version 5.9.4 has a remote integer overflow vulnerability via a crafted certificate with an RSASSA-PSS signature. For example, this can trigger from an unrelated self-signed CA certificate sent by an initiator. Remote code execution cannot occur.

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CVE-2021-41990 is the case number for this vulnerability, which has a CVSS v3.1 base score of 7.5.

Additionally, the in-memory certificate cache in strongSwan before version 5.9.4 has a remote integer overflow vulnerability upon receiving many requests with different certificates to fill the cache and later trigger the replacement of cache entries. The code attempts to select a less-often-used cache entry by means of a random number generator, but this is not done correctly. This could lead to a denial of service (DoS) condition. Remote code execution can’t end up excluded completely, but it would require attackers to have control over the dereferenced memory, so it is very unlikely.

Schneider Bold

CVE-2021-41991 is the case number for this vulnerability, which has a CVSS v3.1 base score of 7.5.

Vulnerable Products

Siemens reports the following products suffer from the vulnerabilities:

  • Siemens RUGGEDCOM RM1224 LTE(4G) EU (6GK6108-4AM00-2BA2): < V7.1
  • Siemens SCALANCE M874-3 (6GK5874-3AA00-2AA2): < V7.1
  • Siemens SCALANCE M876-3 (EVDO) (6GK5876-3AA02-2BA2): < V7.1
  • Siemens SCALANCE M876-3 (ROK) (6GK5876-3AA02-2EA2): < V7.1
  • Siemens SCALANCE M876-4 (EU) (6GK5876-4AA00-2BA2): < V7.1
  • Siemens SCALANCE M876-4 (NAM) (6GK5876-4AA00-2DA2): < V7.1
  • Siemens SCALANCE MUM853-1 (EU) (6GK5853-2EA00-2DA1): < V7.1
  • Siemens SCALANCE MUM856-1 (EU) (6GK5856-2EA00-3DA1): < V7.1
  • Siemens SCALANCE MUM856-1 (RoW) (6GK5856-2EA00-3AA1): < V7.1
  • Siemens SCALANCE S615 (6GK5615-0AA00-2AA2): < V7.1
  • Siemens SCALANCE SC622-2C (6GK5622-2GS00-2AC2): < V2.3 (CVE-2021-41991)
  • Siemens RUGGEDCOM RM1224 LTE(4G) NAM (6GK6108-4AM00-2DA2): < V7.1
  • Siemens SCALANCE SC632-2C (6GK5632-2GS00-2AC2): < V2.3 (CVE-2021-41991)
  • Siemens SCALANCE SC636-2C (6GK5636-2GS00-2AC2): < V2.3 (CVE-2021-41991)
  • Siemens SCALANCE SC642-2C (6GK5642-2GS00-2AC2): < V2.3 (CVE-2021-41991)
  • Siemens SCALANCE SC646-2C (6GK5646-2GS00-2AC2): < V2.3 (CVE-2021-41991)
  • Siemens SIMATIC CP 1242-7 V2 (6GK7242-7KX31-0XE0): < V3.3.46 (CVE-2021-41991)
  • Siemens SIMATIC CP 1243-1 (6GK7243-1BX30-0XE0): < V3.3.46 (CVE-2021-41991)
  • Siemens SIMATIC CP 1243-7 LTE EU (6GK7243-7KX30-0XE0): < V3.3.46 (CVE-2021-41991)
  • Siemens SIMATIC CP 1243-7 LTE US (6GK7243-7SX30-0XE0): < V3.3.46 (CVE-2021-41991)
  • Siemens SIMATIC CP 1243-8 IRC (6GK7243-8RX30-0XE0): < V3.3.46 (CVE-2021-41991)
  • Siemens SIMATIC CP 1542SP-1 (6GK7542-6UX00-0XE0): < V2.2.28 (CVE-2021-41991)
  • Siemens SCALANCE M804PB (6GK5804-0AP00-2AA2): < V7.1
  • Siemens SIMATIC CP 1542SP-1 IRC (6GK7542-6VX00-0XE0): < V2.2.28 (CVE-2021-41991)
  • Siemens SIMATIC CP 1543-1 (6GK7543-1AX00-0XE0): < V2.2.28 (CVE-2021-41991)
  • Siemens SIMATIC CP 1543SP-1 (6GK7543-6WX00-0XE0): < V2.2.28 (CVE-2021-41991)
  • Siemens SIMATIC CP 1545-1 (6GK7545-1GX00-0XE0): < V1.1 (CVE-2021-41991)
  • Siemens SINEMA Remote Connect Server: < V3.1 (CVE-2021-41991)
  • Siemens SIPLUS ET 200SP CP 1542SP-1 IRC TX RAIL (6AG2542-6VX00-4XE0): < V2.2.28 (CVE-2021-41991)
  • Siemens SIPLUS ET 200SP CP 1543SP-1 ISEC (6AG1543-6WX00-7XE0): < V2.2.28 (CVE-2021-41991)
  • Siemens SIPLUS ET 200SP CP 1543SP-1 ISEC TX RAIL (6AG2543-6WX00-4XE0): < V2.2.28 (CVE-2021-41991)
  • Siemens SIPLUS NET CP 1242-7 V2 (6AG1242-7KX31-7XE0): < V3.3.46 (CVE-2021-41991)
  • Siemens SIPLUS NET CP 1543-1 (6AG1543-1AX00-2XE0): < V3.0.22 (CVE-2021-41991)
  • Siemens SCALANCE M812-1 ADSL-Router (Annex A) (6GK5812-1AA00-2AA2): < V7.1
  • Siemens SIPLUS S7-1200 CP 1243-1 (6AG1243-1BX30-2AX0): < V3.3.46 (CVE-2021-41991)
  • Siemens SIPLUS S7-1200 CP 1243-1 RAIL (6AG2243-1BX30-1XE0): < V3.3.46 (CVE-2021-41991)
  • Siemens SCALANCE M812-1 ADSL-Router (Annex B) (6GK5812-1BA00-2AA2): < V7.1
  • Siemens SCALANCE M816-1 ADSL-Router (Annex A) (6GK5816-1AA00-2AA2): < V7.1
  • Siemens SCALANCE M816-1 ADSL-Router (Annex B) (6GK5816-1BA00-2AA2): < V7.1
  • Siemens SCALANCE M826-2 SHDSL-Router (6GK5826-2AB00-2AB2): < V7.1
  • Siemens SCALANCE M874-2 (6GK5874-2AA00-2AA2): < V7.1
Critical Manufacturing Sector

The product sees use mainly in the critical manufacturing sector, and on a global basis.

No exploit targets these vulnerabilities. However, an attacker could leverage these low complexity vulnerabilities.

Siemens has identified the following specific workarounds and mitigations users can apply to reduce risk:

  • RUGGEDCOM RM1224 LTE(4G) EU (6GK6108-4AM00-2BA2), RUGGEDCOM RM1224 LTE(4G) NAM (6GK6108-4AM00-2DA2), SCALANCE M804PB (6GK5804-0AP00-2AA2), SCALANCE M812-1 ADSL-Router (Annex A) (6GK5812-1AA00-2AA2), SCALANCE M812-1 ADSL-Router (Annex B) (6GK5812-1BA00-2AA2), SCALANCE M816-1 ADSL-Router (Annex A) (6GK5816-1AA00-2AA2), SCALANCE M816-1 ADSL-Router (Annex B) (6GK5816-1BA00-2AA2), SCALANCE M826-2 SHDSL-Router (6GK5826-2AB00-2AB2), SCALANCE M874-2 (6GK5874-2AA00-2AA2), SCALANCE M874-3 (6GK5874-3AA00-2AA2), SCALANCE M876-3 (EVDO) (6GK5876-3AA02-2BA2), SCALANCE M876-3 (ROK) (6GK5876-3AA02-2EA2), SCALANCE M876-4 (EU) (6GK5876-4AA00-2BA2), SCALANCE M876-4 (NAM) (6GK5876-4AA00-2DA2), SCALANCE MUM853-1 (EU) (6GK5853-2EA00-2DA1), SCALANCE MUM856-1 (EU) (6GK5856-2EA00-3DA1), SCALANCE MUM856-1 (RoW) (6GK5856-2EA00-3AA1), SCALANCE S615 (6GK5615-0AA00-2AA2): Update to V7.1 or later version 
  • (CVE-2021-41991) SIMATIC CP 1242-7 V2 (6GK7242-7KX31-0XE0), SIMATIC CP 1243-1 (6GK7243-1BX30-0XE0), SIMATIC CP 1243-7 LTE EU (6GK7243-7KX30-0XE0), SIMATIC CP 1243-7 LTE US (6GK7243-7SX30-0XE0), SIMATIC CP 1243-8 IRC (6GK7243-8RX30-0XE0), SIMATIC CP 1542SP-1 (6GK7542-6UX00-0XE0), SIMATIC CP 1543-1 (6GK7543-1AX00-0XE0), SIMATIC CP 1545-1 (6GK7545-1GX00-0XE0), SIPLUS NET CP 1242-7 V2 (6AG1242-7KX31-7XE0), SIPLUS NET CP 1543-1 (6AG1543-1AX00-2XE0), SIPLUS S7-1200 CP 1243-1 (6AG1243-1BX30-2AX0), SIPLUS S7-1200 CP 1243-1 RAIL (6AG2243-1BX30-1XE0): Only deploy certificates via TIA portal that ended up created with TIA portal
  • (CVE-2021-41991) SIMATIC CP 1542SP-1 (6GK7542-6UX00-0XE0), SIMATIC CP 1542SP-1 IRC (6GK7542-6VX00-0XE0), SIMATIC CP 1543SP-1 (6GK7543-6WX00-0XE0), SIPLUS ET 200SP CP 1542SP-1 IRC TX RAIL (6AG2542-6VX00-4XE0), SIPLUS ET 200SP CP 1543SP-1 ISEC (6AG1543-6WX00-7XE0), SIPLUS ET 200SP CP 1543SP-1 ISEC TX RAIL (6AG2543-6WX00-4XE0): Update to V2.2.28 or later version 
  • (CVE-2021-41991) SIMATIC CP 1242-7 V2 (6GK7242-7KX31-0XE0), SIMATIC CP 1243-1 (6GK7243-1BX30-0XE0), SIMATIC CP 1243-7 LTE EU (6GK7243-7KX30-0XE0), SIMATIC CP 1243-7 LTE US (6GK7243-7SX30-0XE0), SIMATIC CP 1243-8 IRC (6GK7243-8RX30-0XE0), SIPLUS NET CP 1242-7 V2 (6AG1242-7KX31-7XE0), SIPLUS S7-1200 CP 1243-1 (6AG1243-1BX30-2AX0), SIPLUS S7-1200 CP 1243-1 RAIL (6AG2243-1BX30-1XE0): Update to V3.3.46 or later version 
  • (CVE-2021-41991) SIMATIC CP 1545-1 (6GK7545-1GX00-0XE0): Update to V1.1 or later version 
  • (CVE-2021-41991) SINEMA Remote Connect Server: Update to V3.1 or later version 
  • (CVE-2021-41991) SCALANCE SC622-2C (6GK5622-2GS00-2AC2), SCALANCE SC632-2C (6GK5632-2GS00-2AC2), SCALANCE SC636-2C (6GK5636-2GS00-2AC2), SCALANCE SC642-2C (6GK5642-2GS00-2AC2), SCALANCE SC646-2C (6GK5646-2GS00-2AC2): Update to V2.3 or later version 
  • (CVE-2021-41991) SIMATIC CP 1543-1 (6GK7543-1AX00-0XE0), SIPLUS NET CP 1543-1 (6AG1543-1AX00-2XE0): Update to V3.0.22 or later version 
More Information

As a general security measure, Siemens recommends protecting network access to devices with appropriate mechanisms. To operate the devices in a protected IT environment, Siemens recommends configuring the environment according to Siemens’ operational guidelines for industrial security and following recommendations in the product manuals.

For more information, click on the Siemens security advisory SSA-539476 in HTML and CSAF.

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