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CVE-2025-9086 Siemens CVE debrief

CVE-2025-9086 is a high-severity curl cookie handling flaw described in Siemens and CISA advisories. Under a specific secure-cookie-to-cleartext transition, curl can read past a heap buffer boundary while comparing cookie paths. The supplied advisory text says the result can be a crash or an incorrect comparison outcome, and the issue is rated with a CVSS 3.1 score of 7.5 because it can disrupt availability.

Vendor
Siemens
Product
RUGGEDCOM RST2428P (6GK6242-6PA00)
CVSS
HIGH 7.5
CISA KEV
Not listed in stored evidence
Original CVE published
2025-09-12
Original CVE updated
2026-09-14
Advisory published
2025-09-12
Advisory updated
2026-09-14

Who should care

Siemens OT asset owners, plant operators, and security teams responsible for the affected Siemens product families listed in the advisory, especially environments running firmware versions older than V3.3 and any deployment that may exercise curl-based HTTP(S) cookie handling.

Technical summary

The flaw is an out-of-bounds heap read in curl's cookie path comparison logic. The supplied description says it can occur when a cookie is first set securely over HTTPS for a host, then the same host is later reached over cleartext HTTP and the same cookie name is set again with path '/'. Instead of ignoring the insecure update, the comparison can read beyond the allocated path buffer, which may crash the process or lead to incorrect cookie handling. The advisory rates the impact as availability-focused rather than confidentiality or integrity.

Defensive priority

High. This is a remotely reachable, unauthenticated issue with potential for denial of service in affected Siemens environments, and the vendor guidance is to move to the fixed release line as soon as feasible.

Recommended defensive actions

  • Update affected Siemens products to V3.3 or later, per the vendor remediation guidance.
  • Use the Siemens and CISA advisory product lists to confirm which devices and firmware versions are actually in scope before scheduling remediation.
  • Prioritize exposed or internet-reachable management interfaces and any systems that rely on web-based cookie handling.
  • Monitor affected devices for unexpected crashes, service restarts, or instability during HTTP/HTTPS interactions.
  • Track the Siemens ProductCERT and CISA advisory pages for any scope clarifications or follow-on updates.

Evidence notes

CISA's CSAF republication for ICSA-26-043-06 was published on 2026-01-28 and updated on 2026-02-25. The supplied source metadata says the issue is a cookie path comparison bug in curl that can read outside a heap buffer boundary, and the remediation is to update affected products to V3.3 or later. The supplied CVSS vector is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Sources and references

Verified primary and authoritative sources

  • CVE-2025-9086 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2025-9086

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2025-9086 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2025-9086

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Source item URL

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/cisagov/CSAF/develop/csaf_files/OT/white/2026/icsa-26-043-06.json

    cisa_csaf

  • Source reference

    Unverified legacy reference

    URL: https://cert-portal.siemens.com/productcert/csaf/ssa-089022.json

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://cert-portal.siemens.com/productcert/html/ssa-089022.html

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/news-events/ics-advisories/icsa-26-043-06

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/news-events/ics-alerts/ics-alert-10-301-01

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/resources-tools/resources/ics-recommended-practices

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/topics/industrial-control-systems

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/sites/default/files/recommended_practices/NCCIC_ICS-CERT_Defense_in_Depth_2016_S508C.pdf

    Reference

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.