CVE-2026-110972 in Płatnik
Summary
by MITRE • 10/30/2026
Płatnik performs client-side authentication. An attacker with access to any application instance connected to the backend server can bypass the login verification process and authenticate as an arbitrary user.
This issue was fixed in metric 242 in version 10.02.002.
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Analysis
by VulDB Data Team • 10/30/2026
The vulnerability identified within the Płatnik software represents a critical failure in client-side authentication mechanisms, fundamentally undermining the integrity of the application's access control model. In secure system design, authentication must always be enforced on the server side to ensure that identity verification is performed by a trusted component with full visibility into security policies and user credentials. By relying on client-side logic for this process, Płatnik introduced a severe architectural flaw where the trust boundary was incorrectly placed at the end-user's device rather than within the backend infrastructure. This misconfiguration allows an attacker who has gained access to any application instance connected to the backend server to manipulate or bypass the login verification steps entirely. The core technical issue lies in the assumption that client-side checks are sufficient for security, ignoring the reality that clients operate in untrusted environments where code can be intercepted, modified, or executed independently of the intended flow.
From a technical perspective, this flaw enables an attacker to authenticate as any arbitrary user without possessing valid credentials. By intercepting network traffic or modifying local application state, the adversary can send requests directly to the backend server that appear to have passed authentication checks. Since the server does not perform its own rigorous verification of these client-side assertions before granting access, it accepts the manipulated request as legitimate. This effectively nullifies the purpose of user accounts and session management within the system. The vulnerability is particularly dangerous in multi-tenant or shared hosting environments where multiple application instances connect to a single backend, as compromise of any one instance can lead to unauthorized access across the entire ecosystem.
The operational impact of this vulnerability is severe, potentially leading to full account takeover for all users within the affected Płatnik deployment. An attacker could impersonate administrators to modify sensitive data, exfiltrate confidential information, or execute malicious actions on behalf of legitimate users. In the context of financial or administrative software like Płatnik, such unauthorized access can result in significant financial loss, regulatory non-compliance, and irreversible damage to organizational reputation. The ability to act as an arbitrary user means that audit trails become unreliable, making forensic analysis difficult after a breach occurs. Furthermore, because the bypass does not require brute-forcing passwords or exploiting complex injection flaws, it is easily exploitable by attackers with basic knowledge of web application security principles.
This vulnerability aligns closely with CWE-287 Improper Authentication and CWE-345 Insufficient Verification of Data Authenticity as defined in the Common Weakness Enumeration database. The failure to verify data authenticity on the server side means that the system cannot guarantee that requests originate from authenticated entities. In terms of the MITRE ATT&CK framework, this flaw facilitates techniques related to Credential Access and Privilege Escalation, specifically allowing an attacker to bypass authentication controls (T1078) and potentially escalate privileges if administrative accounts are targeted. The lack of server-side validation also impacts accountability, as actions taken by impersonated users cannot be reliably attributed to the actual actor behind the attack.
To mitigate this vulnerability, it is essential that all authentication logic be moved exclusively to the server side. Client applications should never make decisions regarding user identity or access rights; their role is limited to presenting a user interface and transmitting credentials securely via encrypted channels such as HTTPS. The backend must independently validate every login attempt against its own secure credential store using strong hashing algorithms and multi-factor authentication where applicable. Additionally, implementing robust session management with short-lived tokens and strict validation of session identifiers can further reduce the risk of hijacking or manipulation. Organizations running affected versions should immediately upgrade to version 10.02.002 or later, which addresses this issue in metric 242. Until patching is complete, network-level controls such as Web Application Firewalls (WAFs) may provide limited protection by inspecting and blocking anomalous request patterns that indicate authentication bypass attempts, though they are not a substitute for fixing the underlying code flaw.