CVE-2026-71969 in OP-TEE
Summary
by MITRE • 08/10/2026
OP-TEE OS through 4.10.0, fixed in commit 7b8b494, contains a buffer underwrite vulnerability in the RSA NOPAD encrypt and decrypt operations within the mbedTLS software backend and SE050 hardware driver that allows a malicious Trusted Application to corrupt secure-world heap memory by supplying an input length exceeding the RSA modulus size. When src_len exceeds rsa_len, the subtraction expression wraps to a large unsigned value, causing a subsequent memcpy to write attacker-controlled data before the destination buffer in S-EL1 secure-world heap memory.
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Analysis
by VulDB Data Team • 08/10/2026
The vulnerability described represents a critical buffer underwrite condition affecting OP-TEE OS versions through 4.10.0, specifically within the cryptographic implementation layer that interfaces with mbedTLS software backend and SE050 hardware driver components. This flaw manifests during RSA NOPAD encryption and decryption operations where insufficient input validation allows malicious Trusted Applications to manipulate memory layout in the secure world environment. The vulnerability stems from improper bounds checking when processing cryptographic inputs, creating a scenario where attacker-controlled data can overwrite heap memory preceding the intended destination buffer.
The technical mechanism of this vulnerability operates through a specific arithmetic underflow condition that occurs when comparing input length against RSA modulus size. When the source length parameter exceeds the RSA key length, the subtraction operation between these values produces an unsigned integer overflow resulting in a large positive value. This corrupted calculation then propagates to subsequent memory copy operations where the system attempts to write data at an address calculated from this erroneous offset. The consequence is that attacker-controlled data gets written to memory locations preceding the target buffer within the S-EL1 secure-world heap memory space, effectively corrupting adjacent heap metadata and potentially enabling arbitrary code execution or information disclosure.
This vulnerability directly maps to CWE-121 Stack-based Buffer Overflow and CWE-787 Out-of-bounds Write within the Common Weakness Enumeration framework, representing a classic buffer management flaw that can escalate to privilege escalation. The operational impact extends beyond simple memory corruption as it provides malicious actors with potential access to sensitive cryptographic operations and secure data processing functions. Attackers could leverage this vulnerability to gain unauthorized access to cryptographic keys stored in secure memory, compromise the integrity of encrypted communications, or potentially execute arbitrary code within the secure execution environment.
The security implications of this flaw align with tactics and techniques documented in the MITRE ATT&CK framework under T1059 Command and Control and T1547 Privilege Escalation. The vulnerability enables adversaries to manipulate heap memory structures and potentially bypass security boundaries that separate trusted and untrusted execution contexts. Organizations deploying OP-TEE OS versions prior to the fix must consider immediate remediation strategies including firmware updates, code patches, and runtime monitoring solutions to detect potential exploitation attempts. The SE050 hardware driver component adds additional complexity as it may require specific firmware updates or driver modifications beyond the standard operating system patching procedures.
The vulnerability demonstrates a fundamental weakness in secure memory management practices within cryptographic implementations, where assumptions about input validation and boundary checking fail to account for edge cases in cryptographic parameter handling. The fix implemented in commit 7b8b494 addresses this by enforcing proper length validation before arithmetic operations and ensuring that memory copy operations respect the intended buffer boundaries. Security teams should implement comprehensive monitoring for heap corruption indicators and establish robust input validation controls across all cryptographic interfaces to prevent similar vulnerabilities from emerging in other components of the secure execution environment.