The vulnerability identified as CVE-2026-26746 affects OpenSourcePOS version 3.4.1 and involves a Local File Inclusion (LFI) flaw in the Sales.php::getInvoice() function. This function improperly handles the Invoice Type configuration, allowing an attacker to manipulate this parameter to include and read arbitrary files from the web server. LFI vulnerabilities typically enable attackers to access sensitive files such as configuration files, credentials, or logs, which can lead to further compromise. In this case, the LFI can be chained with the software's file upload functionality—classified under CWE-434, which relates to unrestricted file upload—to escalate the attack to Remote Code Execution (RCE). This means an attacker could potentially upload malicious code and execute it on the server, gaining full control. The vulnerability has a CVSS v3.1 base score of 8.8, reflecting its high severity due to network attack vector, low attack complexity, required privileges, and no user interaction needed. The impact includes full compromise of confidentiality, integrity, and availability of the affected system. Although no known exploits are currently reported in the wild, the presence of both LFI and file upload weaknesses makes this a critical issue for organizations relying on OpenSourcePOS for their point-of-sale operations. The lack of available patches at the time of reporting increases the urgency for mitigations.

If exploited, this vulnerability can lead to severe consequences for organizations using OpenSourcePOS 3.4.1. Attackers can read sensitive files on the server, potentially exposing credentials, configuration data, and other confidential information. By chaining the LFI with the file upload vulnerability, attackers can achieve Remote Code Execution, allowing them to execute arbitrary code with the privileges of the web server process. This can result in full system compromise, data theft, disruption of point-of-sale operations, financial fraud, and potential lateral movement within the network. The availability of the POS system may be disrupted, impacting business continuity and customer trust. Given the critical role of POS systems in retail and hospitality sectors, exploitation could lead to significant financial losses and reputational damage. The requirement for some privileges to exploit the vulnerability suggests insider threats or compromised accounts could be leveraged. The absence of known exploits in the wild currently provides a window for proactive defense, but the risk remains high due to the ease of exploitation and potential impact.

Organizations should immediately assess their use of OpenSourcePOS 3.4.1 and prioritize mitigating this vulnerability. Since no official patch is currently available, the following specific actions are recommended: 1) Restrict and monitor file upload functionality to allow only necessary file types and implement strict server-side validation and sanitization to prevent malicious files from being uploaded. 2) Harden the Sales.php::getInvoice() function by validating and sanitizing the Invoice Type parameter to prevent path traversal or inclusion of unintended files. 3) Implement web application firewalls (WAF) with rules to detect and block LFI attempts and suspicious file upload activity. 4) Limit privileges of the web server process to minimize the impact of potential code execution. 5) Conduct regular audits of server logs to detect unusual file access patterns or uploads. 6) Isolate the POS system network segment to reduce lateral movement risk. 7) Prepare incident response plans specific to POS system compromise. 8) Monitor vendor communications for patches or updates and apply them promptly once available. 9) Educate staff about the risks of privilege misuse and enforce strong access controls. These targeted measures go beyond generic advice by focusing on the specific vulnerable components and attack vectors involved.