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CVE-2025-25253 Siemens CVE debrief

CVE-2025-25253 is a high-severity certificate-validation issue (CWE-297) published by CISA on 2025-05-13 and later republished based on Siemens ProductCERT updates. The source description says an unauthenticated attacker in a man-in-the-middle position may intercept and tamper with connections to the ZTNA proxy. For defenders, the key takeaway is that trust validation at the proxy layer is at risk, so affected deployments should be treated as sensitive until the vendor-specific remediation is confirmed and applied. The source record also contains a notable text mismatch: the advisory metadata identifies Siemens RUGGEDCOM APE1808, while the vulnerability description and remediation text reference FortiProxy/FortiOS and FortiGate NGFW; verify the exact fixed version guidance in the official Siemens advisory before acting.

Vendor
Siemens
Product
RUGGEDCOM APE1808
CVSS
HIGH 7.5
CISA KEV
Not listed in stored evidence
Original CVE published
2025-05-13
Original CVE updated
2026-02-12
Advisory published
2025-05-13
Advisory updated
2026-02-12

Who should care

OT/ICS security teams, network defenders, and administrators responsible for Siemens RUGGEDCOM APE1808 deployments or any environment relying on the affected ZTNA proxy path.

Technical summary

The advisory record maps CVE-2025-25253 to an improper validation of a certificate with host mismatch (CWE-297). In the supplied source text, this can allow an attacker positioned in the communication path to intercept and tamper with ZTNA proxy connections. The source CVSS vector is CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H, indicating high impact if the trust failure is exploitable in the local network context described by the record.

Defensive priority

High. The issue is rated CVSS 7.5 and affects certificate trust on proxy traffic, which can expose confidential data and permit tampering if an attacker can place themselves in the path.

Recommended defensive actions

  • Confirm whether your Siemens RUGGEDCOM APE1808 deployment is in scope for ICSA-25-135-01 / SSA-864900.
  • Use the official Siemens ProductCERT advisory to verify the exact fixed version or mitigation steps, because the embedded remediation text in the source item is inconsistent with the Siemens product naming.
  • Prioritize patching or mitigation before exposing the affected path to untrusted or poorly controlled networks.
  • Review network segmentation and routing so that adversaries cannot easily position themselves as a man-in-the-middle on proxy traffic.
  • Monitor for certificate-trust failures and unexpected proxy connection anomalies during validation and after remediation.

Evidence notes

Source evidence comes from the CISA CSAF record for ICSA-25-135-01 and the linked Siemens ProductCERT advisory SSA-864900. The CSAF revision history shows CVE-2025-25253 was added in Additional Release 4 on 2025-11-11, and the latest CISA republication occurred on 2026-02-12. The record also shows a text inconsistency: the affected product metadata names Siemens RUGGEDCOM APE1808, while the vulnerability description and remediation text refer to FortiProxy/FortiOS and FortiGate NGFW. That mismatch means the vendor-specific fix details should be verified directly against the official Siemens links before use.

Official resources

Publicly disclosed on 2025-05-13 via CISA ICSA-25-135-01. CVE-2025-25253 was added to the advisory in the 2025-11-11 Additional Release 4, and CISA republished the advisory on 2026-02-12 based on Siemens ProductCERT SSA-864900 updates.