Vulnerability · Published Apr 24, 2026 · Assigned by GitHub_M
CVE-2026-33662OP-TEE: RSASSA EMSA- PKCS1-v1_5 underflow in emsa_pkcs1_v1_5_encode()
High 7.5
In plain English
A high-severity integer overflow in optee_os from OP-TEE. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 35% of all known vulnerabilities).
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:13 | optee-os | no fix listed | DEBIAN-CVE-2026-33662 |
| Ubuntu:25.10 | optee-os | no fix listed | UBUNTU-CVE-2026-33662 |
| Ubuntu:26.04:LTS | optee-os | no fix listed | UBUNTU-CVE-2026-33662 |
| Ubuntu:26.10 | optee-os | no fix listed | UBUNTU-CVE-2026-33662 |
Affected products (as reported)
Weakness: CWE-190 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
- https://github.com/OP-TEE/optee_os/security/advisories/GHSA-4cf8-v5g3-73gr x_refsource_CONFIRM