CVE-2026-53763: OP-TEE AES-GCM Integer Overflow – Authentication Tag Failure

Technical summary

The vulnerability arises from 32-bit integer overflows in OP-TEE core's AES-GCM authentication tag computation logic. AES-GCM (Galois/Counter Mode) is an authenticated encryption scheme that produces a cryptographic tag to verify both confidentiality and authenticity of data. The overflow occurs in bit-length calculations after processing cumulative payload or Additional Authenticated Data (AAD) exceeding 512 MB. Due to the integer overflow, the tag is computed against incorrect bit-length parameters, breaking the cryptographic guarantee that an unmodified ciphertext will always produce the same tag. This is a pure integrity failure; decryption of captured ciphertexts remains intractable without the key.

Business impact

The practical impact depends on deployment context. For systems using OP-TEE to protect sensitive operations (payment processing, DRM, biometric authentication), a weakened authentication tag could allow an attacker to craft forged encrypted messages that pass validation. This undermines the trust model of the TEE. However, impact is constrained: the attacker must have local access to interact with OP-TEE, and the overflow threshold of 512 MB is high for typical single-request payloads. Organizations relying on OP-TEE for cryptographic assurance should prioritize patching, but the risk is lower than for remote network-accessible TEE flaws.

Affected systems

OP-TEE versions 3.0.0 through 4.10.x are vulnerable. Version 4.11.0 and later are patched. The TEE runs on ARM Cortex-A processors with TrustZone support—common in mobile devices, IoT platforms, and enterprise ARM-based systems. Affected deployments include Android devices, automotive platforms, and edge computing appliances that bundle OP-TEE as their trusted execution layer. The source is Trusted Firmware (trustedfirmware op-tee).

Exploitability

Exploitability is limited by access and scale requirements. An attacker must have local access to the device and the ability to send crafted encrypted data to OP-TEE. They must also engineer a scenario where a single AES-GCM operation processes >512 MB of payload or AAD—a high bar for most real-world use cases. The CVSS score of 3.8 (LOW) reflects these constraints: Attack Vector is Local, and the integrity impact is isolated (only authentication fails, not confidentiality). No public exploits or KEV listing exist; this is not an actively exploited vulnerability.

Remediation

Upgrade OP-TEE to version 4.11.0 or later. Verify the upgrade path with your platform vendor (e.g., ARM, device manufacturer, or your secure boot integrator), as OP-TEE updates often require coordinated changes to bootloaders and kernel modules. No workarounds are available for earlier versions. If immediate patching is not possible, limit exposure by restricting which applications can invoke AES-GCM operations through OP-TEE's access control policies.

Patch guidance

Upgrade to OP-TEE version 4.11.0 or later. Obtain the patch from the Trusted Firmware project (trustedfirmware.org). Integration steps: (1) Download the patched source or binary for your ARM platform; (2) coordinate with your boot firmware and kernel maintainers to ensure compatibility; (3) rebuild secure boot images if required; (4) test cryptographic operations (especially those handling >100 MB payloads) before production deployment. Verify that your device's firmware release notes list this CVE fix.

Detection guidance

Detection is challenging because the flaw manifests as silent cryptographic failure rather than crashes or logs. Monitor for: (1) unexpected authentication tag mismatches in application logs; (2) unexplained validation errors in services using OP-TEE for AES-GCM; (3) version inventory of OP-TEE across your fleet—query secure firmware version APIs if available. Network-based detection is unlikely because communication with OP-TEE is local. Consider enabling debug logging in OP-TEE (if security policy permits) to track tag computation errors during testing.

Why prioritize this

Despite the LOW CVSS score, prioritize this patch in Q3 2026 if you operate devices running OP-TEE 3.0–4.10 in roles handling encrypted data. The flaw is in core crypto, and even though it requires local access and high-volume payloads, it directly compromises authentication integrity—a foundational TEE guarantee. Organizations with strict crypto compliance (FIPS, PCI-DSS, automotive functional safety) should treat it as medium priority. For general mobile and consumer deployments with routine OP-TEE usage, it is lower priority relative to other patches, but should be included in the next scheduled firmware update.

Risk score, explained

CVSS 3.8 (LOW) is justified: the vulnerability is local-only (no remote trigger), requires privilege (User scope broadens the attack surface, but still local), and causes integrity loss without affecting confidentiality or availability in the classical sense. The attack is technically feasible but operationally constrained by the 512 MB threshold and the need for local attack setup. The lack of public exploitation or KEV listing confirms it is not currently weaponized.

Frequently asked questions