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CVE-2026-33662— OP-TEE: RSASSA EMSA- PKCS1-v1_5 underflow in emsa_pkcs1_v1_5_encode()

Quick assessment

Affected
OP-TEE optee_os
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

OP-TEE Trusted OS是OP-TEE开源的一个实现 Arm TrustZone 技术的开源可信执行环境（TEE）。 OP-TEE Trusted OS 3.8.0版本至4.10版本存在输入验证错误漏洞，该漏洞源于emsa_pkcs1_v1_5_encode()函数中填充大小计算可能溢出，导致memset()调用覆盖内存直至OP-TEE崩溃。

CVSS 7.5 · High EPSS 0.57% · P46
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I. Basic Information for CVE-2026-33662

Vulnerability Information
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Vulnerability Title
OP-TEE: RSASSA EMSA- PKCS1-v1_5 underflow in emsa_pkcs1_v1_5_encode()
Source: CVE Program / CVE List V5
Vulnerability Description
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. From 3.8.0 to 4.10, in the function emsa_pkcs1_v1_5_encode() in core/drivers/crypto/crypto_api/acipher/rsassa.c, the amount of padding needed, "PS size", is calculated by subtracting the size of the digest and other fields required for the EMA-PKCS1-v1_5 encoding from the size of the modulus of the key. By selecting a small enough modulus, this subtraction can overflow. The padding is added as a string of 0xFF bytes with a call to memset(), and an underflowed integer will cause the memset() call to overwrite until OP-TEE crashes. This only affects platforms registering RSA acceleration.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
整数溢出或超界折返
Source: CVE Program / CVE List V5
Vulnerability Title
OP-TEE Trusted OS 输入验证错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
OP-TEE Trusted OS是OP-TEE开源的一个实现 Arm TrustZone 技术的开源可信执行环境（TEE）。 OP-TEE Trusted OS 3.8.0版本至4.10版本存在输入验证错误漏洞，该漏洞源于emsa_pkcs1_v1_5_encode()函数中填充大小计算可能溢出，导致memset()调用覆盖内存直至OP-TEE崩溃。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
OP-TEE optee_os >= 3.8.0, <= 4.10 -

II. Public POCs for CVE-2026-33662

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III. Intelligence Information for CVE-2026-33662

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Vendor Advisories for CVE-2026-33662 (1)

IV. Related Vulnerabilities

Same product: optee_os
Same vendor: OP-TEE
Same weakness: CWE-190

V. Comments for CVE-2026-33662

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