CVE-2026-81576 in CodeMeter Runtime
Summary
by MITRE • 08/27/2026
If configured as a server, CodeMeter Runtime before versions 8.41a and 9.10 issues handles per connection and relies on a cryptographically weak SID as sole authenticator. An attacker can brute-force the SID, recover another session's handle number, and read license information belonging to another handle.
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Analysis
by VulDB Data Team • 08/27/2026
The vulnerability in CodeMeter Runtime versions prior to 8.41a and 9.10 represents a critical failure in authentication mechanisms when the software is deployed as a server component. The core technical flaw lies in the reliance on a Session Identifier, or SID, which serves as the sole authenticator for client connections. This SID is generated using a cryptographically weak algorithm that lacks sufficient entropy, making it predictable and susceptible to brute-force attacks. In standard secure architectures, session identifiers must be randomly generated with high complexity to prevent prediction. However, in this implementation, the limited space of possible SIDs allows an attacker to systematically iterate through potential values until a valid one is discovered. This fundamental weakness undermines the integrity of the connection establishment process, as possession of a valid SID grants immediate access without requiring additional credentials or cryptographic proofs.
The operational impact of this vulnerability extends beyond simple unauthorized access. Once an attacker successfully brute-forces a valid SID, they gain the ability to recover handle numbers associated with active sessions. In the context of CodeMeter, handles are references used by the runtime environment to manage license keys and digital rights management data. By correlating the guessed SID with specific handle numbers, an adversary can target existing connections that have already been authenticated through other means or simply exploit the weak authentication layer directly. This capability allows for session hijacking, where the attacker impersonates a legitimate client within an active communication stream. The ability to read license information belonging to another handle constitutes a severe confidentiality breach, potentially exposing proprietary software licensing structures and enabling unauthorized usage of protected intellectual property.
This vulnerability aligns with several established industry standards regarding security flaws. It is classified under CWE-384, which denotes Session Fixation, although the mechanism here leans more heavily toward CWE-290, Authentication Bypass by Spoofing, due to the predictability of the SID. Furthermore, from a tactical perspective within the MITRE ATT&CK framework, this behavior corresponds to T1567, Evading End-Point Detection, as it involves manipulating session identifiers to bypass standard authentication controls. The exploitation technique also reflects aspects of T1078, Valid Accounts, since the attacker effectively assumes the identity of a valid user by guessing their session token. These classifications highlight that the issue is not merely a coding error but a systemic design flaw in how state and identity are managed during server-client interactions.
Mitigation strategies must address both the immediate technical weakness and broader architectural practices. The primary remediation involves upgrading to CodeMeter Runtime version 8.41a or later, where this specific authentication logic has been corrected. For environments that cannot immediately upgrade, network-level controls such as strict firewall rules limiting access to only trusted IP addresses can reduce the attack surface by preventing external brute-force attempts. Additionally, implementing rate-limiting on connection requests and enforcing multi-factor authentication for administrative interfaces can provide compensating controls against credential guessing attacks. Long-term architectural improvements should mandate the use of cryptographically secure random number generators for all session identifiers, ensuring that SIDs are sufficiently long and unpredictable to resist statistical analysis or brute-force enumeration. Regular security audits focusing on state management and token generation practices are essential to prevent similar vulnerabilities in future deployments.