OP-TEE: RSASSA EMSA- PKCS1-v1_5 underflow in emsa_pkcs1_v1_5_encode()

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Summary

CVECVE-2026-33662
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-24 19:17:09 UTC
Updated2026-04-24 19:17:09 UTC
DescriptionOP-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.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Problem Types: CWE-190 | CWE-190 CWE-190: Integer Overflow or Wraparound

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA OP-TEE Optee Os affected >= 3.8.0, <= 4.10 Not specified

References

ReferenceSourceLinkTags
github.com/OP-TEE/optee_os/security/advisories/GHSA-4cf8-v5g3-73gr [email protected] github.com
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