CVE-2026-114622 baserproject CVE debrief

Who should care

Defenders of baserCMS installations, particularly those using the BcThemeFile plugin, should assess exposure and apply patches to prevent exploitation. This includes reviewing system logs for suspicious activity, restricting access to the Admin API, and monitoring for potential code execution and arbitrary file writes.

Why it matters

Defenders should prioritize verifying exposure and applying patches, as an authenticated administrator can write PHP files into writable locations, exceeding the intended theme-template editing boundary.

• An authenticated administrator can write PHP files into writable locations such as webroot and execute them
• Exceeding the intended theme-template editing boundary
• Potential for code execution and arbitrary file writes

Technical summary

The optional BcThemeFile plugin's Admin API validates a raw path in ThemeFilesService::update() and getFullpath(), but ThemeFileForm::_execute() subsequently applies rawurldecode() to fullpath before writing. This check-before-decode ordering allows percent-encoded traversal to pass containment checks and become a path outside the theme directory at the write sink. An authenticated administrator can write PHP files into writable locations such as webroot and execute them, exceeding the intended theme-template editing boundary.

Defensive priority

Defenders should prioritize verifying exposure and applying patches, as an authenticated administrator can write PHP files into writable locations.

Recommended defensive actions

• Verify exposure by checking if the BcThemeFile plugin is enabled and if the version is vulnerable
• Apply patches to update to version 5.3.2 or 5.4.2
• Restrict access to the Admin API to prevent authenticated administrators from exploiting the vulnerability
• Monitor for suspicious activity, such as unexpected PHP file writes or executions
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The source identifies a check-before-decode ordering in ThemeFilesService::update() and getFullpath(), and ThemeFilesService::copy(), allowing percent-encoded traversal to pass containment checks. This vulnerability is a result of the plugin's flawed path validation and decoding process. The source also notes that exploitation requires the non-default plugin, an administrator session, and a same-origin Origin header.

Sources and references

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.