CVE-2026-53210: Linux Kernel TEE Shared Memory Leak – MEDIUM Severity

Technical summary

The vulnerability exists in register_shm_helper() within the kernel's TEE shared memory subsystem. The function allocates a shared memory (shm) structure, then calls iov_iter_npages() to validate the memory range. If iov_iter_npages() returns 0—which occurs when the caller specifies a zero-length buffer in struct tee_ioctl_shm_register_data—the error handling jumps to the err_ctx_put label. However, err_ctx_put does not free the previously allocated shm structure, resulting in a CWE-401 (Missing Release of Memory after Effective Lifetime) condition. The fix redirects the error path to err_free_shm, ensuring proper cleanup.

Business impact

Resource exhaustion from repeated exploitation can degrade performance on systems running TEE workloads, particularly those handling cryptographic operations, secure payment processing, or other sensitive tasks delegated to the trusted execution environment. On resource-constrained embedded or IoT devices with TEE support, this could trigger out-of-memory conditions and system instability. However, the vulnerability requires local access and unprivileged user-level permissions, limiting blast radius in typical enterprise environments.

Affected systems

The Linux kernel across all versions with TEE shared memory support are affected. This includes systems with ARM TrustZone, Intel SGX integration, or other TEE implementations that expose the TEE_IOC_SHM_REGISTER ioctl to user space. Affected deployments include Linux distributions running on Arm-based SoCs, IoT gateways, and systems with TEE security coprocessors. Verify your kernel version and TEE subsystem configuration against the vendor advisory for precise patched versions.

Exploitability

Exploitability is straightforward but operationally limited. Any local unprivileged user can trigger the leak by calling ioctl(TEE_IOC_SHM_REGISTER) with a zero-length buffer. No special privileges, kernel-mode access, or complex race conditions are required. However, practical impact depends on system resources and monitoring; a single leak is negligible, but sustained triggering in a loop could exhaust memory and cause denial of service. No known public exploits exist, and the vulnerability is not listed in CISA's Known Exploited Vulnerabilities catalog.

Remediation

Apply the kernel patch that corrects the error path in register_shm_helper() to jump to err_free_shm instead of err_ctx_put, ensuring the allocated shm structure is freed on validation failure. Verify the patch against the official Linux kernel repository or your distribution's security advisory. For systems that cannot be patched immediately, restrict TEE_IOC_SHM_REGISTER access via SELinux, AppArmor, or seccomp policies to trusted applications only.

Patch guidance

Monitor your Linux distribution's security advisories for a kernel update addressing CVE-2026-53210. Verify patch applicability by checking kernel version and TEE subsystem enablement in your build configuration. Most major distributions (Red Hat, Debian, Ubuntu, SUSE) will release updates through their standard channels. Test patches in a staging environment before production deployment, particularly on systems with active TEE workloads, to ensure no regression in TEE functionality.

Detection guidance

Monitor kernel memory usage patterns on systems with active TEE subsystems, particularly for unexplained growth in kernel slab allocators. Audit TEE_IOC_SHM_REGISTER ioctl calls via seccomp logging or strace on suspicious processes. Check /proc/meminfo and dmesg for out-of-memory killer invocations or allocation failures in the tee subsystem. System administrators should establish baseline memory profiles for their TEE workloads and alert on anomalies.

Why prioritize this

Although CVSS 5.5 (Medium) reflects the local-only access requirement and lack of confidentiality or integrity impact, the vulnerability warrants moderate priority because it affects kernel stability on TEE-capable platforms and requires no privilege escalation. Organizations running mission-critical TEE workloads (mobile payments, secure enclaves, hardware security) should prioritize patching. Low-risk for pure cloud or non-TEE systems.

Risk score, explained

The CVSS 3.1 score of 5.5 (MEDIUM) reflects: Attack Vector Local (requires shell or application access), Attack Complexity Low (trivial to trigger via ioctl), Privileges Required Low (any user can call the ioctl), User Interaction None, Scope Unchanged, and Availability Impact High (resource exhaustion). Confidentiality and Integrity impacts are None because the leak does not expose data or enable privilege escalation. The score appropriately captures a denial-of-service risk limited to local attackers on systems with TEE enabled.

Frequently asked questions