Buffer overflow in Op-Tee Optee OS
CVE-2026-40257
OP-TEE is a Trusted Execution Environment (TEE) designed as companion to a non-secure Linux kernel running on Arm; Cortex-A cores using the TrustZone technology. Starting in version 3.21.0 and prior to version 4.11.0, the ARM Crypto Extensions accelerated SHA-3 implementation has an off-by-one error that can cause a massive heap overflow that corrupts all TEE kernel memory following the hash state. This affects all platforms built with `CFG_CRYPTO_WITH_CE82=y` (ARMv8.2+ with SHA3 Crypto Extensions). Version 4.11.0 contains a patch. As a workaround, disable SHA3 Crypto Extensions with `CFG_CRYPTO_WITH_CE82=n`.
Vulnerability class: Buffer Overflow
EPSS: 0.001 (1.4th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.
Affected products
- Op-tee Optee_os — versions >= 3.21.0, < 4.11.0
- Trustedfirmware Op-tee
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Patch, Mitigation, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-40257?
- CVE-2026-40257 is a medium-severity vulnerability in Op-Tee Optee OS, classified under Out-of-bounds Write. CVSS score: 5.5/10. Published 2026-07-06.
- How severe is CVE-2026-40257?
- Medium severity. CVSS v3 base score is 5.5 out of 10.