CVE-2026-41228: Froxlor has Local File Inclusion via path traversal in API `def_language` parameter leads to Remote Code Execution

Should you act?

Critical, preconditions apply

Severe if exploited, but exploitation needs conditions that may not apply to you. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
• EPSS 0.7%, percentile 54: FIRST’s model estimates a 0.7% chance of exploitation activity in the next 30 days, higher than 54% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
• Needs an account (low (any account)). Exposure depends on who can log in.
• Only applies if your dependency tree includes froxlor/froxlor (Composer (PHP)) <= 2.3.5, fixed in 2.3.6. Check your lockfile, including transitive dependencies.

What it is

Froxlor is open source server administration software. Prior to version 2.3.6, the Froxlor API endpoint Customers.update (and Admins.update) does not validate the deflanguage parameter against the list of available language files. An authenticated customer can set deflanguage to a path traversal payload (e.g., ../../../../../var/customers/webs/customer1/evil), which is stored in the database. On subsequent requests, Language::loadLanguage() constructs a file path using this value and executes it via require, achieving arbitrary PHP code execution as the web server user. Version 2.3.6 fixes the issue.

From the GitHub advisory

Summary

The Froxlor API endpoint Customers.update (and Admins.update) does not validate the deflanguage parameter against the list of available language files. An authenticated customer can set deflanguage to a path traversal payload (e.g., ../../../../../var/customers/webs/customer1/evil), which is stored in the database. On subsequent requests, Language::loadLanguage() constructs a file path using this value and executes it via require, achieving arbitrary PHP code execution as the web server user.

Details

Root cause: The API and web UI have inconsistent validation for the deflanguage parameter.

The web UI (customerindex.php:261, adminindex.php:265) correctly validates deflanguage against Language::getLanguages(), which scans the lng/ directory for actual language files:

Weakness type: CWE-98.

Product: froxlor/froxlor (Composer (PHP)) · Assigned by: GitHub_M · Published: 2026-04-23

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: low (any account)
• User interaction: none
• Scope: changed (can affect other components)

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation poc, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.75% probability of exploitation activity in the next 30 days; percentile 54.

Timeline

• 2026-04-16 — GitHub-reviewed advisory GHSA-w59f-67xm-rxx7 published (critical)
• 2026-04-23 — CVE record last updated
• 2026-04-23 — CVE record published by GitHub_M

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-w59f-67xm-rxx7 github.com
2. CVE.org record CVE-2026-41228 cve.org
3. NVD entry CVE-2026-41228 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com

Critical Composer (PHP) advisories · Today’s Security Digest