CVE-2026-44362 Overview
CVE-2026-44362 affects OP-TEE, an open-source Trusted Execution Environment (TEE) that runs alongside a non-secure Linux kernel on Arm Cortex-A cores using TrustZone technology. Versions from 3.20.0 up to (but not including) 4.11.0 contain a flaw in the subkey rollback protection mechanism. The shdr_load_pub_key() function in core/crypto/signed_hdr.c parses subkey headers but fails to populate the subkey_version field on the runtime shdr_pub_key structure. As a result, revoked or downgraded subkey chains can sign Trusted Applications (TAs) that OP-TEE will load without triggering rollback protection. Version 4.11.0 contains the patch.
Critical Impact
A local attacker with the ability to install signed TAs can bypass rollback protection and load Trusted Applications signed with revoked or older subkeys, undermining TA authentication integrity.
Affected Products
- TrustedFirmware OP-TEE versions 3.20.0 through 4.10.x
- OP-TEE mainline configurations using subkey-based TA signing chains
- Devices relying on ree_fs_ta for Trusted Application loading
Discovery Timeline
- 2026-07-06 - CVE-2026-44362 published to NVD
- 2026-07-07 - Last updated in NVD database
Technical Details for CVE-2026-44362
Vulnerability Analysis
The flaw resides in OP-TEE's Trusted Application authentication pipeline, categorized as Improper Authorization [CWE-285]. When OP-TEE parses a signed header containing a subkey, shdr_load_pub_key() in core/crypto/signed_hdr.c extracts header fields but omits assignment of the subkey_version value to the runtime shdr_pub_key structure. Consequently, key->version remains zero regardless of the version declared in the header.
The zeroed version propagates downstream. When ree_fs_ta_open() in core/kernel/ree_fs_ta.c invokes check_update_version(), it passes the zero value to the rollback database. The database only advances when it receives a non-zero, higher version, so it never records progress. This effectively neutralizes rollback protection and allows TAs signed with revoked or older subkey chains to load.
Root Cause
The root cause is a missing field assignment during subkey header parsing. Header versioning data exists on disk but is discarded during in-memory construction of the public key structure. Because the rollback database logic relies on this field to detect downgrade attempts, the omission silently disables the entire subkey rollback protection subsystem.
Attack Vector
Exploitation requires local access with privileges to load a Trusted Application into OP-TEE. An attacker with a previously valid but now-revoked subkey, or an older subkey superseded by a newer version, can sign a malicious or outdated TA. OP-TEE accepts the TA because check_update_version() never observes a version high enough to reject the load. The vulnerability impacts integrity of the TEE trust boundary without directly affecting confidentiality or availability.
No verified public exploit code is available. See the GitHub Security Advisory GHSA-fhcg-pp56-8v75 for upstream technical details.
Detection Methods for CVE-2026-44362
Indicators of Compromise
- Trusted Application loads succeeding with subkey versions that should have been revoked by the rollback database
- Rollback database entries for subkey versions that never advance past zero despite header claims of higher versions
- Presence of OP-TEE builds identifying as versions between 3.20.0 and 4.10.x on production devices
Detection Strategies
- Audit OP-TEE build metadata across the device fleet to identify versions in the 3.20.0 to 4.10.x range
- Inspect TA signing chains for use of subkeys that were expected to be retired or superseded
- Instrument or log calls to check_update_version() to observe whether non-zero subkey versions are ever recorded
Monitoring Recommendations
- Monitor secure boot and TEE telemetry for unexpected TA load events tied to legacy signing keys
- Track firmware provenance and version reporting from field devices through device management platforms
- Correlate TA installation events with the identity of the signing subkey to detect use of deprecated chains
How to Mitigate CVE-2026-44362
Immediate Actions Required
- Upgrade OP-TEE to version 4.11.0 or later, which contains the fix for shdr_load_pub_key()
- Rebuild and redeploy firmware images incorporating the patched OP-TEE across affected devices
- Rotate and re-sign Trusted Applications using current subkeys after upgrading
Patch Information
OP-TEE version 4.11.0 propagates the subkey_version field into the runtime shdr_pub_key structure so that check_update_version() receives correct values. Refer to the OP-TEE Security Advisory GHSA-fhcg-pp56-8v75 for release details and commit references.
Workarounds
- No known workarounds are available according to the upstream advisory; upgrading to OP-TEE 4.11.0 is required
- Restrict physical and local administrative access to devices until firmware upgrades are deployed
- Limit provisioning of Trusted Applications to trusted build pipelines and enforce current subkey usage at the signing stage
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
