CVE-2026-40257

OP-TEE has SHA-3 accelerated finalize heap overflow

5.5 Medium

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.

Attack profile

How easy it is to exploit

Attack vector: Local
Complexity: Low
Privileges needed: Low
User interaction: None

What an attacker can affect

Confidentiality: None
Integrity: None
Availability: High

Exploit likelihood

0.15%Unchanged since Jul 7, 2026

What each source reports

CVE List Score used 5.5

OP-TEE has SHA-3 accelerated finalize heap overflow

Record: CVE-2026-40257
CVSS 3.1: 5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-787
Updated: 2026-11-02

EUVDEUVD-2026-41891 5.5

Record: EUVD-2026-41891
CVSS 3.1: 5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

NVD 5.5

Record: CVE-2026-40257
CVSS 3.1: 5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-787
Updated: 2026-11-02

OSV 5.5

OP-TEE has SHA-3 accelerated finalize heap overflow

Record: CVE-2026-40257
CVSS 3.1: 5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-787
Updated: 2026-11-02

OSVDEBIAN-CVE-2026-40257 5.5

Record: DEBIAN-CVE-2026-40257
CVSS 3.1: 5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVUBUNTU-CVE-2026-40257 5.5

Record: UBUNTU-CVE-2026-40257
CVSS 3.1: 5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`optee-os` Debian:13	All versions, plus listed versions 4.10.0-14.10.0-24.5.0-24.7.0-14.8.0-14.9.0-1	None known
`optee-os` Ubuntu:25.10	All versions, plus listed versions 4.5.0-14.5.0-24.7.0-1	None known
`optee-os` Ubuntu:26.10	All versions, plus listed versions 4.8.0-14.10.0-14.10.0-2	None known
`optee-os` Ubuntu:26.04:LTS	All versions, plus listed versions 4.7.0-14.8.0-1	None known

History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-40257 is a medium vulnerability (CVSS 5.5) in Trustedfirmware Op-tee, published July 6, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.15%, the 4th percentile. No source names a fixed version.