CVE-2018-3891 in Home Camera 27US
Summary
by MITRE
An exploitable firmware downgrade vulnerability exists in the firmware update functionality of Yi Home Camera 27US 1.8.7.0D. A specially crafted file can cause a logic flaw, resulting in a firmware downgrade. An attacker can insert an SD card to trigger this vulnerability.
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Analysis
by VulDB Data Team • 06/04/2023
The vulnerability described in CVE-2018-3891 represents a critical firmware downgrade flaw affecting the Yi Home Camera 27US model running firmware version 1.8.7.0D. This issue resides within the camera's firmware update mechanism and demonstrates a fundamental security weakness in the device's update validation process. The vulnerability allows an attacker to manipulate the firmware update procedure through a specially crafted file, potentially enabling unauthorized firmware version rollbacks. The attack vector is particularly concerning as it requires only physical access to the device through SD card insertion, making it accessible to attackers with minimal technical expertise. This weakness directly impacts the device's security posture by potentially allowing the installation of older firmware versions that may contain known vulnerabilities or backdoors. The flaw operates at the firmware level, bypassing traditional software-based security controls and exploiting a logic error in the update validation routine.
The technical implementation of this vulnerability stems from inadequate validation mechanisms within the camera's firmware update functionality. When an SD card containing a maliciously crafted firmware file is inserted, the device's update process fails to properly verify the firmware version being installed. This logic flaw allows the system to accept and install firmware versions that are older than the currently running version, effectively enabling a downgrade attack. The vulnerability manifests as a failure in the firmware version comparison logic, where the device does not properly enforce version hierarchy checks during the update process. This type of flaw falls under CWE-239, which describes weaknesses in firmware update mechanisms, and specifically relates to inadequate validation of firmware components. The attack requires physical access to the device and can be executed through simple file manipulation on an SD card, making it particularly dangerous in environments where devices may be physically accessible to unauthorized parties.
The operational impact of this vulnerability extends beyond simple firmware manipulation to potentially compromise the entire security ecosystem of the affected camera. Firmware downgrades can restore previously patched vulnerabilities, effectively reverting security improvements that were implemented in newer firmware versions. This creates a significant risk for users who may unknowingly install compromised firmware versions that contain known exploits or backdoors. The vulnerability undermines the device's ability to maintain a secure baseline, as attackers can potentially install firmware versions that lack security features or contain intentional malicious code. From an attacker's perspective, this vulnerability provides a persistent entry point that can be exploited without requiring network access or complex attack chains. The implications are particularly severe given that this is a camera device, which typically operates in private environments where physical access may be more easily obtained than network-based attacks.
Mitigation strategies for this vulnerability must address both the immediate security risk and the underlying architectural weaknesses that enabled the flaw. Device manufacturers should implement robust firmware version validation mechanisms that enforce strict version hierarchies and prevent downgrade operations. The most effective approach involves implementing cryptographic signature verification for all firmware updates, ensuring that only legitimately signed firmware versions can be installed. Additionally, the update process should include integrity checks and version validation that cannot be bypassed through simple file manipulation. Security patches should be deployed immediately to address the specific logic flaw in the firmware update validation routine. Users should be advised to avoid inserting unknown SD cards into their devices and to ensure that firmware updates are only performed through official channels. This vulnerability highlights the importance of secure firmware update mechanisms and aligns with ATT&CK technique T1072, which covers software deployment and execution through legitimate system tools. Organizations should also consider implementing firmware integrity monitoring solutions that can detect unauthorized firmware modifications and alert security teams to potential compromise.