An off‑by‑one error in the accelerated SHA‑3 finalize routine of OP‑TEE’s ARM Crypto Extensions causes a massive heap overflow that corrupts all TEE kernel memory after the hash state. The overflow can overwrite critical internal data structures or code, exposing the trusted environment to potential compromise. The weakness is a classic out‑of‑bounds write (CWE‑787).

OP‑TEE OS versions starting from 3.21.0 up to the release preceding 4.11.0 are vulnerable when the accelerated SHA‑3 path is enabled via the configuration flag CFG_CRYPTO_WITH_CE82=y. The issue applies to ARM Cortex‑A platforms supporting ARMv8.2+ TrustZone and the SHA‑3 Crypto Extensions. The0.

The CVSS score of 5.5 indicates moderate severity. The EPSS score of <1% and the absence from the CISA KEV catalog suggest that exploitation has not been observed at scale. An attacker would need to execute code within the trusted environment—either through a malicious trusted application or from the host side—to trigger the SHA‑3 finalize with crafted input that triggers the overflow.