Froxlor up to 2.3.11 ACME Client AcmeSh.php FileDir::safe_exec letsencryptchallengepath os command injection

Summaryinfo

A vulnerability classified as very critical was found in Froxlor up to 2.3.11. Affected is the function FileDir::safe_exec of the file lib/Froxlor/Cron/Http/LetsEncrypt/AcmeSh.php of the component ACME Client. Executing a manipulation of the argument letsencryptchallengepath can lead to os command injection. This vulnerability is tracked as CVE-2026-100714. The attack can be launched remotely. No exploit exists. Upgrading the affected component is advised.

Detailsinfo

A vulnerability classified as very critical was found in Froxlor up to 2.3.11. This vulnerability affects the function FileDir::safe_exec of the file lib/Froxlor/Cron/Http/LetsEncrypt/AcmeSh.php of the component ACME Client. The manipulation of the argument letsencryptchallengepath with an unknown input leads to a os command injection vulnerability. The CWE definition for the vulnerability is CWE-78. The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

Froxlor before 2.3.12 does not restrict or escape the system.letsencryptchallengepath setting: unlike sibling settings hardened in GHSA-33mp, the field has no string_regexp or required_otp guard, and its value is concatenated unescaped into the acme.sh command line built in lib/Froxlor/Cron/Http/LetsEncrypt/AcmeSh.php and executed by the root cron via FileDir::safe_exec. Because safe_exec only blacklists shell metacharacters such as ; | & > < \ $ ~ ?, spaces and quotes survive and the value is word-split into additional acme.sh arguments. An administrator, or any actor able to write settings (for example through the settings-import API), can therefore inject acme.sh options such as --renew-hook, --pre-hook or --post-hook to obtain arbitrary command execution as root at the next Let's Encrypt cron run, or use --config-home/--cert-home for arbitrary file writes. Versions up to and including 2.3.10 are affected; the issue is fixed in 2.3.12.

The advisory is available at github.com. This vulnerability was named CVE-2026-100714 since 09/26/2026. The exploitation appears to be easy. The attack can be initiated remotely. Additional levels of successful authentication are required for exploitation. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 09/26/2026). This vulnerability is assigned to T1202 by the MITRE ATT&CK project.

By approaching the search of inurl:lib/Froxlor/Cron/Http/LetsEncrypt/AcmeSh.php it is possible to find vulnerable targets with Google Hacking.

Upgrading to version 2.3.12 eliminates this vulnerability.

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Productinfo

Name

• Froxlor

Version

• 2.3.0
• 2.3.1
• 2.3.2
• 2.3.3
• 2.3.4
• 2.3.5
• 2.3.6
• 2.3.7
• 2.3.8
• 2.3.9
• 2.3.10
• 2.3.11

License

• open-source

Website

• Product: https://github.com/froxlor/froxlor/

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