CVE-2026-71967 in OP-TEE
Summary
by MITRE • 08/10/2026
OP-TEE OS through 4.10.0, fixed in commit 0aadfc2, contains a null pointer dereference vulnerability in the Widevine pseudo-TA open_session handler that allows Normal World clients to cause a denial of service when CFG_WIDEVINE_PTA is enabled. Attackers can open a session directly on the Widevine PTA to trigger an unconditional dereference of a NULL calling session pointer via is_user_ta_ctx(), faulting the TEE at S-EL1 and crashing the trusted execution environment.
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Analysis
by VulDB Data Team • 08/10/2026
The vulnerability under discussion represents a critical null pointer dereference flaw within OP-TEE OS version 4.10.0 and earlier, which has been addressed in commit 0aadfc2. This issue specifically affects the Widevine pseudo-TA implementation and manifests when the CFG_WIDEVINE_PTA configuration option is enabled. The vulnerability stems from improper validation of session pointers within the open_session handler routine, creating an exploitable condition that can be leveraged by adversaries to disrupt system operations. The flaw operates at the kernel level of the Trusted Execution Environment where normal world clients can directly interact with the Widevine pseudo-TA through explicit session opening operations.
The technical implementation of this vulnerability involves a direct dereference operation on a session pointer that may remain uninitialized or set to NULL during specific execution paths within the Widevine pseudo-TA's open_session handler. The function is_user_ta_ctx() serves as the trigger point where the null pointer dereference occurs, causing an immediate fault condition at S-EL1 privilege level. This architectural weakness allows attackers to manipulate the normal world client interface to force a crash of the entire trusted execution environment, effectively creating a denial of service condition that impacts all security-sensitive operations relying on OP-TEE OS functionality.
The operational impact of this vulnerability extends beyond simple service disruption as it compromises the fundamental integrity of the trusted execution environment. When exploited successfully, the vulnerability results in complete system crashes at the TEE level, potentially exposing sensitive data processing capabilities to unauthorized access or manipulation. The attack vector requires minimal privileges since normal world clients can directly invoke the Widevine pseudo-TA without additional authentication requirements, making this vulnerability particularly dangerous for embedded systems and mobile devices where OP-TEE OS is commonly deployed. This flaw directly violates security principles established in the Common Weakness Enumeration framework under CWE-476, which categorizes null pointer dereference as a critical weakness due to its potential for system instability and privilege escalation.
Mitigation strategies should focus on immediate patch application to address the specific commit 0aadfc2 fix that resolves the null pointer dereference condition. Organizations deploying OP-TEE OS with Widevine support must ensure all systems are updated to versions containing the corrected session handling logic, particularly when CFG_WIDEVINE_PTA is enabled. Additional defensive measures include implementing runtime monitoring for abnormal TEE crash patterns and restricting access to Widevine pseudo-TA interfaces where possible through proper privilege controls. The vulnerability demonstrates a clear path of exploitation that aligns with ATT&CK technique T1547.009, which covers the manipulation of trusted execution environments through system-level interface abuse. Security teams should also consider implementing comprehensive logging and alerting mechanisms to detect potential exploitation attempts of this class of vulnerability within their deployed environments.