CVE-2026-71268: OpenPLC Runtime v3 Path Traversal in Structured Text FILE Directive Leading to Arbitrary File Write

Severity: critical (CVSS 9.9 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-05 · updated 2026-10-24
Weakness: CWE-22

Description

OpenPLC Runtime v3's compile_program function (webserver/openplc.py) parses directives from uploaded Structured Text (.st) program files and writes the referenced content to with no validation that file_path stays within the ./core directory. A path-validation function, validate_file_path, exists elsewhere in the codebase (webserver/credentials.py) but is never invoked from compile_program, leaving the sink unprotected.

Affected products

thiagoralves OpenPLC_v3: all versions

References

https://github.com/thiagoralves/OpenPLC_v3
https://github.com/thiagoralves/OpenPLC_v3/blob/master/webserver/openplc.py

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