CVE-2016-8276 in USG2100
Summary
by MITRE
Buffer overflow in the Point-to-Point Protocol over Ethernet (PPPoE) module in Huawei USG2100, USG2200, USG5100, and USG5500 unified security gateways with software before V300R001C10SPC600, when CHAP authentication is configured on the server, allows remote attackers to cause a denial of service (server restart) or execute arbitrary code via crafted packets sent during authentication.
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Analysis
by VulDB Data Team • 09/22/2022
The vulnerability identified as CVE-2016-8276 represents a critical buffer overflow flaw within the Point-to-Point Protocol over Ethernet implementation of Huawei's unified security gateways. This issue affects multiple models including the USG2100, USG2200, USG5100, and USG5500 series devices operating with firmware versions prior to V300R001C10SPC600. The vulnerability specifically manifests during CHAP authentication processes on the server side, creating a pathway for malicious actors to exploit the system through carefully crafted network packets. The buffer overflow occurs within the PPPoE module's handling of authentication data, where insufficient input validation allows attackers to overwrite adjacent memory regions through malformed packet structures.
The technical nature of this vulnerability aligns with CWE-121, which describes buffer overflow conditions where insufficient bounds checking permits data to be written beyond the allocated buffer space. The flaw operates at the network protocol level where the PPPoE server component fails to properly validate the length and content of authentication packets received from clients. When CHAP authentication is enabled, the system processes challenge-response exchanges that include user credentials and authentication tokens. Attackers can construct packets that exceed the expected buffer boundaries, causing memory corruption that leads to unpredictable system behavior. The vulnerability's exploitation potential stems from the fact that the buffer overflow can be triggered without authentication, as the flaw exists in the protocol handling layer itself rather than requiring valid credentials.
The operational impact of CVE-2016-8276 extends beyond simple denial of service to encompass potential code execution capabilities, making it particularly dangerous for network security infrastructure. Remote attackers can leverage this vulnerability to either force system restarts, thereby disrupting network services and potentially causing availability issues for critical infrastructure, or to execute arbitrary code on the affected devices. This latter capability represents a significant escalation as it allows attackers to gain unauthorized control over the security gateway, potentially enabling them to modify firewall rules, intercept traffic, or establish persistent access points within the network. The vulnerability affects devices that serve as primary security controls in enterprise and organizational networks, making the potential impact substantial.
Mitigation strategies for this vulnerability require immediate firmware updates from Huawei to address the buffer overflow in the PPPoE module. Organizations should prioritize patching affected devices with the latest security releases, particularly those containing the V300R001C10SPC600 or later firmware versions. Network administrators should also implement temporary network segmentation measures to limit exposure while patches are deployed, including disabling CHAP authentication on affected devices when possible and monitoring for suspicious authentication traffic patterns. The vulnerability's characteristics align with ATT&CK technique T1210, which involves exploiting vulnerabilities in remote services to gain system access. Security monitoring should focus on detecting anomalous PPPoE authentication attempts and unusual traffic patterns that might indicate exploitation attempts. Additionally, implementing network access control lists to restrict PPPoE traffic to trusted sources can provide additional defense in depth measures against this specific attack vector.