CVE-2026-81159 in Commerce CyberSource Plugin
Summary
by MITRE • 09/02/2026
Observable Timing Discrepancy vulnerability in Drupal Commerce CyberSource allows Brute Force. This issue affects Commerce CyberSource versions: from 0.0.0 to 1.10.0.
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Analysis
by VulDB Data Team • 09/02/2026
The identified security flaw represents a classic observable timing discrepancy within the integration layer of Drupal Commerce, specifically affecting modules interacting with the CyberSource payment gateway infrastructure. Versions ranging from initial releases up through 1.10.0 are susceptible to this vulnerability due to insufficient constant-time comparison practices when validating cryptographic signatures or authentication tokens provided by the external payment processor. In secure software design, particularly in systems handling financial transactions and sensitive credentials, string comparisons must execute in a time-independent manner to prevent attackers from deducing valid secrets through side-channel analysis. When an application compares user-supplied input against stored secrets using standard equality operators that short-circuit upon finding the first mismatched character, it inadvertently leaks information about how many characters of the secret are correct based on the response latency observed by the client.
This architectural weakness enables a brute force attack vector where an adversary can systematically guess valid authentication credentials or transaction signatures byte-by-byte. By measuring the precise time taken for the server to reject invalid requests versus accept them, even with minor network jitter accounted for through statistical averaging, an attacker can reconstruct the secret key or token required to impersonate legitimate transactions. This capability undermines the integrity of the payment processing workflow, allowing malicious actors to potentially forge transaction approvals, bypass fraud detection mechanisms embedded within the CyberSource integration, and execute unauthorized financial operations under the guise of a valid merchant account session.
From a classification perspective, this vulnerability aligns with CWE-208, which defines Observable Timing Discrepancy as an issue where timing information can be used to infer secret data. It also maps closely to CWE-354 regarding Improper Validation of Integrity Check Value if the discrepancy allows for bypassing signature verification logic. In terms of offensive security frameworks such as MITRE ATT&CK, this technique falls under Tactic TA0006 Credential Access and specifically relates to techniques involving side-channel attacks or brute forcing authentication mechanisms when proper cryptographic safeguards are absent. The exploitation does not require complex buffer overflows or injection payloads but relies instead on precise network timing measurements and iterative request generation against the vulnerable endpoint handling CyberSource callbacks or webhook validations.
The operational impact of this vulnerability is severe within e-commerce environments that rely heavily on automated payment processing. Successful exploitation could lead to unauthorized refunds, fraudulent chargebacks initiated by attackers who have guessed valid merchant credentials, or manipulation of order statuses without proper authorization. Furthermore, because Drupal Commerce modules often handle customer data and financial records during these interactions, a breach in authentication integrity may expose sensitive personally identifiable information linked to transaction histories. The risk is compounded if the compromised CyberSource API keys possess elevated permissions within the payment gateway provider's ecosystem, potentially allowing broader access beyond just order processing functions.
Mitigation strategies must prioritize immediate code remediation alongside infrastructure-level controls. Developers should update the Commerce CyberSource module to version 1.10.1 or later where this timing discrepancy has been addressed by implementing constant-time string comparison algorithms for all secret validation processes. Until an updated patch is deployed, administrators can implement rate limiting on endpoints that process payment callbacks and webhook responses to slow down automated brute force attempts significantly. Additionally, enabling strict logging and monitoring for anomalous patterns in request latency or frequency at the web server level can help detect ongoing exploitation attempts. It is also advisable to rotate any exposed API keys immediately if there is suspicion of compromise and to review audit logs from CyberSource for unusual transaction volumes originating from unexpected IP addresses or user agents that may indicate successful credential guessing.