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

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.

Published: 2026-04-24 Last update: 2026-06-05 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-33662 is rated Low Risk (37.1/100): CVSS High severity, with low exploitation likelihood (EPSS 0.07%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-33662

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-04-25 — 0.07% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-33662

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]

Weakness enumeration for CVE-2026-33662

OS Trackers for CVE-2026-33662

vendor priority summary link
debian not yet assigned CVE-2026-33662 not yet assigned priority: Debian including 1 source packages (optee-os), 3 status rows across 3 suites (forky, sid, trixie): resolved 2, open 1. https://security-tracker.debian.org/tracker/CVE-2026-33662
ubuntu medium CVE-2026-33662 medium priority: Ubuntu including 1 source packages (optee-os), 5 status rows across 5 suites (jammy, noble, questing, resolute, upstream): DNE 2, needed 2, needs-triage 1. https://ubuntu.com/security/CVE-2026-33662

Affected software / configurations for CVE-2026-33662

Vendor Product Version Raw CPE
trustedfirmware op-tee >= 3.8.0, <= 4.10.0 cpe:2.3:o:trustedfirmware:op-tee:*:*:*:*:*:*:*:*

References for CVE-2026-33662

cvelogic Threat Intelligence