CVE-2026-40257: op-tee optee_os Out-of-bounds Write
Vulnerability summary
CVE-2026-40257 is a medium (CVSS 5.5) Out-of-bounds Write vulnerability in op-tee optee_os. EPSS estimates a 0.15% chance of exploitation in the next 30 days, higher than 4% of scored vulnerabilities.
Timeline
- 06-07-2026PublishedVulnerability first disclosed.
- 06-07-2026Last modifiedVulnerability information updated.
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. Starting in version 3.21.0 and prior to version 4.11.0, the ARM Crypto Extensions accelerated SHA-3 implementation has an off-by-one error that can cause a massive heap overflow that corrupts all TEE kernel memory following the hash state. This affects all platforms built with `CFG_CRYPTO_WITH_CE82=y` (ARMv8.2+ with SHA3 Crypto Extensions). Version 4.11.0 contains a patch. As a workaround, disable SHA3 Crypto Extensions with `CFG_CRYPTO_WITH_CE82=n`.
CVSS metrics
4 scores · 4 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- NVDNIST5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.15%
Chance of exploitation in the next 30 days
Percentile
4%
Versus all other CVEs
30-day change
0.00 pp
From 0.15% on 20-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Debian1 product
- optee-osAll versions (No fix recorded)
Op-tee1 product
- optee_os≥ 3.21.0, < 4.11.0
Trustedfirmware1 product
- op-tee≥ 3.21.0, ≤ 4.10.0
Ubuntu1 product
- optee-osAll versions (No fix recorded)
4 vendors · 4 products
References
4 links- github.com/OP-TEE/optee_os/security/advisories/GHSA-75x4-j8p9-55qvX Refsource CONFIRMREPORTMitigationPatchVendor Advisory
