CVE-2026-45614: OP-TEE ECDH Private Key Recovery via Curve Validation Bypass

Technical summary

The vulnerability stems from missing validation in OP-TEE's ECDH shared secret derivation. When TEE_DeriveKey is called with a public key, the implementation does not verify that the (X, Y) coordinate pair satisfies the curve equation Y² ≡ X³ + aX + b (mod P). An attacker can supply points that lie on a different, related curve. For each call with a crafted key, the operation leaks d mod r, where d is the private key and r is derived from the mathematical relationship between the legitimate curve and the attacker's chosen curve. Accumulating roughly 30-40 such modular remainders allows reconstruction of d using the Chinese Remainder Theorem. This is a signature verification bypass (CWE-347) in the cryptographic validation layer.

Business impact

Compromise of ECDH private keys undermines forward secrecy, long-term key confidentiality, and any system deriving session secrets from OP-TEE. Organizations deploying OP-TEE for secure key derivation—particularly in IoT, automotive, or financial systems relying on TrustZone—face exposure of sensitive cryptographic material. The attack requires local access, but once executed, the leaked private key can enable decryption of past and future communications, credential forgery, and lateral movement. Systems already using compromised keys may need emergency key rotation and full audit of encrypted data.

Affected systems

OP-TEE versions prior to 4.11.0 are affected. The vulnerability applies to ECDH operations across all supported Arm Cortex-A processors using TrustZone. Devices and systems embedding OP-TEE as their TEE implementation—including but not limited to those using OP-TEE's official builds or vendor-customized variants—require patching. Check your TEE implementation to confirm whether OP-TEE is in use and verify the version number.

Exploitability

The attack requires local access (AV:L) to invoke TEE_DeriveKey and is moderately difficult to execute (AC:H), necessitating precise construction of invalid curve points and multiple calls to leak sufficient key material. However, once an attacker achieves local access, the process is deterministic and does not require user interaction. No network interaction is needed. The barrier is primarily technical sophistication rather than privilege—an unprivileged local user (PR:L) can perform the attack, making it accessible to a broad class of adversaries with device access.

Remediation

Upgrade OP-TEE to version 4.11.0 or later, which adds validation to ensure public keys are points on the correct elliptic curve before deriving shared secrets. Verify the patch directly from the Trusted Firmware project repository or your vendor's security advisory. After patching, conduct cryptographic audit of any keys derived using affected OP-TEE versions, and rotate sensitive material if necessary.

Patch guidance

Update OP-TEE to version 4.11.0 or later. Consult your device vendor or the official Trusted Firmware OP-TEE project for release artifacts and verification procedures. If you maintain custom OP-TEE builds, pull the latest source and rebuild. Test patches in a controlled environment before production deployment, particularly for systems where TEE firmware updates may impact bootloader, firmware attestation, or secure world functionality.

Detection guidance

Identify systems running OP-TEE by checking TEE implementation and version strings in firmware metadata or boot logs. Monitor for repeated TEE_DeriveKey calls with unusual patterns of invalid public keys, though this may be difficult to log from the normal world. Forensic analysis of systems with suspected key compromise should focus on audit trails from applications calling TEE cryptographic functions. Consider implementing integrity checks on keys known to have been derived during the vulnerable period.

Why prioritize this

Although the CVSS score is MEDIUM (4.7), the attack fundamentally breaks ECDH confidentiality and enables full private key recovery. The requirement for local access limits blast radius compared to network attacks, but the deterministic nature of the exploitation, the small number of calls needed (~30-40), and the broad deployment of OP-TEE in embedded and IoT systems warrant prompt patching. Prioritize systems storing long-term keys or deriving session secrets critical to authentication and encryption.

Risk score, explained

CVSS 4.7 reflects local-access-only requirement (AV:L) and moderate technical complexity (AC:H), limiting immediate remote exploitability. However, the 'High' confidentiality impact (C:H) reflects complete compromise of ECDH secrets. The score does not fully capture the cryptographic severity: once the private key is recovered, all security properties of the key are lost. For systems where ECDH keys are foundational to trust, the practical impact may exceed the base score.

Frequently asked questions