Executive brief
OP-TEE is a secure operating system used on Arm-based devices to protect sensitive data and cryptographic operations. A flaw in how it handles certain digital signature tasks allows an attacker to trigger a system crash by providing a specially crafted cryptographic key. This results in a denial-of-service, potentially disrupting secure device operations or causing the entire system to reboot.
Technical details
An integer underflow vulnerability exists in the emsa_pkcs1_v1_5_encode() function within core/drivers/crypto/crypto_api/acipher/rsassa.c. The vulnerability occurs when calculating the padding size (PS size) for RSASSA-PKCS1-v1_5 encoding; specifically, subtracting the digest and metadata sizes from a small RSA modulus results in a negative value stored in an unsigned integer. This underflowed value is subsequently passed to memset(), causing a massive heap overwrite with 0xFF bytes until the Trusted Execution Environment (TEE) crashes. The issue specifically affects platforms with RSA acceleration enabled, such as those using NXP CAAM, HiSilicon ACC_V3, or Versal crypto drivers. A fix is available in OP-TEE version 4.11.0.
Affected products
- TrustedFirmware OP-TEE OS 3.8.0 to 4.10.0
Timeline
- 2025-12-24: other: Report received by vendor
- 2026-01-07: other: Confirmed as security issue
- 2026-04-24: patched: Fix published in version 4.11.0
- 2026-04-24: advisory: Public disclosure