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PatchSiren cyber security CVE debrief

CVE-2021-21704 Festo Didactic SE CVE debrief

CVE-2021-21704 is a PHP Firebird PDO driver flaw that can let a malicious database server trigger crashes in functions such as getAttribute(), execute(), and fetch(). In Festo Didactic SE MES PC deployments that include the affected PHP component, the practical impact is denial of service, with potential memory corruption noted in the advisory.

Vendor
Festo Didactic SE
Product
MES PC
CVSS
MEDIUM 5.9
CISA KEV
Not listed in stored evidence
Original CVE published
2024-02-27
Original CVE updated
2026-01-27
Advisory published
2024-02-27
Advisory updated
2026-01-27

Who should care

Festo MES PC operators, OT/automation teams, and administrators responsible for PHP-based components that connect to Firebird databases, especially where the database server is not fully trusted or is externally reachable.

Technical summary

The advisory says PHP versions 7.3.x below 7.3.29, 7.4.x below 7.4.21, and 8.0.x below 8.0.8 are affected when using the Firebird PDO driver extension. A malicious database server can return invalid response data that the driver does not parse correctly, which can lead to application crashes and denial of service; the source also notes possible memory corruption. CISA’s supplied CVSS vector is CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H (5.9, Medium).

Defensive priority

Moderate: prioritize patching and component verification soon, especially for MES PC deployments that use Firebird PDO or depend on database availability.

Recommended defensive actions

  • Inventory MES PC and related systems to confirm whether PHP is present and whether the Firebird PDO driver is in use.
  • Upgrade PHP to a fixed release at or above 7.3.29, 7.4.21, or 8.0.8, depending on the branch in use.
  • Use Festo’s Factory Control Panel replacement for XAMPP on MES PCs and obtain the current version through Festo technical support.
  • Restrict and segment database connectivity so only trusted servers can reach the affected application.
  • Test the update in a maintenance window and verify database functions continue to work normally after remediation.

Evidence notes

The supplied CISA CSAF advisory ICSA-26-027-02 states that invalid response data from a malicious Firebird database server can crash PHP Firebird PDO functions and cause denial of service, with potential memory corruption. The same advisory ties the issue to PHP 7.3/7.4/8.0 fixed versions and recommends Factory Control Panel as the replacement for XAMPP on MES PCs. The supplied enrichment does not list the issue in CISA KEV.

Sources and references

Verified primary and authoritative sources

  • CVE-2021-21704 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2021-21704

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

  • CVE-2021-21704 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2021-21704

    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-26-027-02.json

    cisa_csaf

  • Source reference

    Unverified legacy reference

    URL: https://festo.csaf-tp.certvde.com/.well-known/csaf/white/2024/fsa-202402.json

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://certvde.com/en/advisories/vendor/festo/

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://festo.com/psirt

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://certvde.com/en/advisories/VDE-2023-065

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/news-events/ics-advisories/icsa-26-027-02

    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

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.