CVE-2026-40257

TEE crash via SHA-3 finalization underflow

Published Jul 6, 2026 · Updated Jul 6, 2026

Heap overflow in OP-TEE OS 3.21.0 through 4.10.0 allows local users to crash the TEE through accelerated SHA-3 finalization. The strict greater-than test in sha3_process() buffers an exact block without compression, so finalization underflows the unsigned padding length passed to memset(). A Trusted Application on an Armv8.2+ build with CFG_CRYPTO_WITH_CE82 enabled can trigger the approximately 4 GB zero-fill, causing an immediate fault and TEE-wide service interruption.

CVSS severity5.5
Medium
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap overflow in OP-TEE OS 3.21.0 through 4.10.0 allows local users to crash the TEE through accelerated SHA-3 finalization. The strict greater-than test in sha3_process() buffers an exact block without compression, so finalization underflows the unsigned padding length passed to memset(). A Trusted Application on an Armv8.2+ build with CFG_CRYPTO_WITH_CE82 enabled can trigger the approximately 4 GB zero-fill, causing an immediate fault and TEE-wide service interruption.

The record

CVE
CVE-2026-40257
Published
Jul 6, 2026
Updated
Jul 6, 2026
Vendor
OP-TEE
Product
OP-TEE OS
Classifications
CWE-787, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 6, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 6, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 3.21.0, < 4.11.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

OP-TEE · OP-TEE OSversion=>= 3.21.0, < 4.11.0

Published CVSS scores

5.5GitHub, Inc.CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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