ICSA-26-134-07: Siemens SIMATIC

CISA's summary

Summary: SIMATIC HMI Unified Comfort Panels before V21.0 are affected by a vulnerability that allows an unauthenticated attacker to access the web browser via the help link. This vulnerability allows an attacker to access the web browser through the Control Panel if it is not protected by the corresponding security mechanisms. This opens the possibility for the attacker to find backdoors, which might lead to unwanted misconfigurations. Siemens has released new versions for the affected products and recommends to update to the latest versions.

Products, as the advisory lists them

DeSpy has not checked any unit, hardware revision or firmware.

Vulnerabilities in this advisory

• CVE-2026-27662 — CVE-2026-27662 · CWE-1188

  Affected devices do not properly restrict access to the web browser via the Control Panel when no corresponding security mechanisms are in place. This could allow an unauthenticated attacker to gain unauthorized access to the web browser, potentially enabling the discovery of backdoors, performing unauthorized actions, or exploiting misconfigurations that may lead to further system compromise.

Acknowledgments, as the advisory lists them

• Siemens ProductCERT: reported this vulnerability to CISA.

The advisory's legal notice

The use of Siemens Security Advisories is subject to the terms and conditions listed on: https://www.siemens.com/productcert/terms-of-use.

Sources

• The advisory at cisa.gov
• The CSAF document (JSON)

DeSpy's copy of this version is dated 2026-09-28.