CVE-2026-58956 in Android
Summary
by MITRE • 11/02/2026
In modpowF4 of avb_rsa.c, there is a possible signature verification bypass due to a logic error in the code. This could lead to local escalation of privilege with no additional execution privileges needed. User interaction is not needed for exploitation.
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Analysis
by VulDB Data Team • 11/02/2026
The vulnerability identified within the avb_rsa.c module specifically affects the modpowF4 function, which serves as a critical component in the Android Verified Boot (AVB) cryptographic verification process. This logic error represents a significant deviation from expected secure coding practices regarding modular exponentiation operations used for RSA signature validation. The core technical flaw lies in how the function handles intermediate states or boundary conditions during the computation of large integer arithmetic, potentially allowing an attacker to manipulate the input data such that the resulting mathematical output falsely satisfies the verification criteria without possessing a valid cryptographic key. This bypass is not merely a theoretical weakness but stems from specific implementation details where edge cases are not adequately sanitized or validated before being processed by the underlying cryptographic engine.
From a classification perspective, this vulnerability aligns with CWE-20 Improper Input Validation and potentially CWE-347 Improper Verification of Cryptographic Signature. The failure to correctly validate inputs against expected constraints allows for an attack vector that undermines the integrity checks designed to protect system boot sequences. By exploiting this logic error, an adversary can craft a malicious payload or modified firmware image that appears cryptographically valid despite lacking proper authorization. This effectively neutralizes one of the primary security layers intended to prevent unauthorized code execution during the device startup phase.
The operational impact of this flaw is severe due to its potential for local privilege escalation. Since Android Verified Boot operates at a low level in the system initialization process, successfully bypassing signature verification grants an attacker control over critical system components before higher-level security mechanisms are fully engaged. The exploitation does not require additional execution privileges on the target system, meaning that even users with limited access or unprivileged accounts can potentially leverage this vulnerability to gain elevated rights. Furthermore, because user interaction is not required for exploitation, the attack surface is significantly widened, allowing for automated attacks via maliciously crafted files placed in accessible directories or through network-exposed services if applicable within specific device configurations.
This type of exploit maps directly to MITRE ATT&CK techniques related to Bootkit and Defense Evasion, specifically those involving tampering with boot configuration data or bypassing signature verification mechanisms. An attacker leveraging this vulnerability could establish persistence at the firmware level, making detection difficult for standard endpoint security solutions that operate above the kernel layer. The ability to escalate privileges without user interaction further exacerbates the risk, as it enables silent compromise of device integrity and confidentiality of sensitive data stored on the platform.
Mitigation strategies must focus on rigorous code review and formal verification of cryptographic implementations within the AVB stack. Developers should ensure that all inputs to modular exponentiation functions are strictly validated against expected ranges and formats before processing. Implementing constant-time algorithms can also help prevent side-channel attacks that might complement this logic error. Additionally, deploying runtime integrity checks and leveraging hardware-backed security features such as Trusted Execution Environments (TEE) or Secure Boot with measured boot practices can provide additional layers of defense. Regular updates to the Android Verified Boot components are essential to address known implementation flaws and maintain a robust security posture against evolving threats targeting system initialization processes.