CVE-2026-53636 in Open edX
Summary
by MITRE • 09/02/2026
Open edX Platform enables the authoring and delivery of online learning at any scale. Prior to commit 3a5ac85, a security vulnerability has been identified in the Open edX LMS platform's LTI (Learning Tools Interoperability) Provider implementation. The validate_timestamp_and_nonce function in lms/djangoapps/lti_provider/signature_validator.py does not validate OAuth nonces or timestamps, allowing an attacker who captures a valid LTI launch request to replay it an unlimited number of times without detection. This issue has been patched via commit 3a5ac85.
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Analysis
by VulDB Data Team • 09/02/2026
The Open edX platform serves as a robust infrastructure for the authoring and delivery of online learning content at scale, relying heavily on interoperability standards such as Learning Tools Interoperability to integrate with external educational tools. Within this ecosystem, the LTI Provider implementation facilitates secure communication between the learning management system and third-party applications by utilizing OAuth-based authentication mechanisms. A critical security flaw was identified in versions prior to commit 3a5ac85, specifically within the signature validation logic located in the lms/djangoapps/lti_provider/signature_validator.py module. This vulnerability stems from a failure in the validate_timestamp_and_nonce function, which is responsible for ensuring that incoming LTI launch requests are both fresh and unique.
The core technical flaw lies in the omission of proper validation checks for OAuth nonces and timestamps. In standard OAuth 1.0a implementations, these elements serve as essential safeguards against replay attacks. The nonce ensures that each request token is used only once, while the timestamp verifies that the request was generated within an acceptable time window to prevent delayed execution by attackers who may have intercepted valid traffic. By failing to validate these parameters, the platform inadvertently allowed any captured LTI launch request to be reused indefinitely. An attacker with network access capable of intercepting HTTP traffic could capture a legitimate authentication payload and replay it multiple times without triggering any security alerts or rejection mechanisms from the server.
From an operational perspective, this vulnerability poses significant risks related to session hijacking and unauthorized access. Since the LTI launch process often establishes user sessions or triggers specific actions within the learning environment, successful replay attacks could allow malicious actors to impersonate legitimate users. This could lead to unauthorized viewing of course materials, manipulation of grades, injection of malicious content into discussions, or other disruptive activities that compromise the integrity and confidentiality of the educational platform. The lack of detection mechanisms means that such intrusions could persist over extended periods without immediate visibility to administrators.
This vulnerability aligns with CWE-294, which describes a security flaw related to authentication bypass due to accepting replayed messages, and is also associated with CWE-310 regarding cryptographic issues involving insufficient validation of nonces or timestamps. In the context of the MITRE ATT&CK framework, this behavior facilitates Replay Attacks (Tactic: Execution or Persistence depending on outcome), where adversaries reuse previously captured valid authentication credentials or tokens to gain unauthorized access without needing to crack passwords or exploit additional software bugs.
The issue has been remediated in commit 3a5ac85 by implementing rigorous validation logic for both nonces and timestamps within the signature validator. To mitigate similar risks, organizations running Open edX should ensure they are operating on patched versions that include this fix. Additionally, administrators should enforce strict network security controls such as TLS encryption to prevent traffic interception in transit. Regular auditing of LTI integration configurations and monitoring for anomalous patterns in launch requests can further enhance the resilience of the platform against replay-based attacks.