CVE-2018-11574 in pppd
Summary
by MITRE
Improper input validation together with an integer overflow in the EAP-TLS protocol implementation in PPPD may cause a crash, information disclosure, or authentication bypass. This implementation is distributed as a patch for PPPD 0.91, and includes the affected eap.c and eap-tls.c files. Configurations that use the `refuse-app` option are unaffected.
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Analysis
by VulDB Data Team • 12/03/2025
The vulnerability identified as CVE-2018-11574 represents a critical security flaw within the Point-to-Point Protocol Daemon (PPPD) implementation of the EAP-TLS protocol. This issue stems from inadequate input validation mechanisms combined with an integer overflow condition that can be exploited to compromise system integrity. The vulnerability specifically affects the eap.c and eap-tls.c source files that are part of PPPD version 0.91, making it a software-level weakness rather than a network protocol flaw. The affected implementation is distributed as a patch, indicating that this represents a known issue that was addressed through software updates, though the vulnerability remains exploitable in unpatched systems.
The technical root cause of this vulnerability lies in the improper handling of input data within the EAP-TLS authentication process. When processing certain malformed input parameters, the PPPD implementation fails to properly validate the size and content of received data structures, leading to potential integer overflow conditions. This occurs during the processing of EAP-TLS packets where the protocol attempts to manage session data and authentication parameters. The integer overflow can result in memory corruption, which manifests as program crashes or unpredictable behavior. According to CWE standards, this vulnerability maps to CWE-190, which describes integer overflow and wraparound conditions that can lead to memory corruption and arbitrary code execution.
The operational impact of CVE-2018-11574 extends beyond simple service disruption to encompass potential information disclosure and authentication bypass capabilities. When exploited, the vulnerability can cause the PPPD service to crash, effectively denying network access to legitimate users who depend on point-to-point connections. More concerning is the potential for information disclosure where attackers might extract sensitive data from memory locations that become corrupted due to the integer overflow. The authentication bypass aspect represents the most severe risk, as it could allow unauthorized users to establish network connections without proper authentication, effectively compromising the security of the entire network infrastructure that relies on EAP-TLS for secure authentication. This aligns with ATT&CK framework techniques related to privilege escalation and credential access through protocol manipulation.
Organizations affected by this vulnerability should prioritize immediate patch deployment to address the integer overflow and input validation issues within their PPPD implementations. The recommended mitigation strategy involves updating to the latest PPPD version that includes the patched eap.c and eap-tls.c files, ensuring that all systems running EAP-TLS authentication are protected. Configuration management should also include monitoring for unauthorized PPPD processes and implementing network segmentation to limit the potential impact of exploitation. The vulnerability's classification as affecting PPPD 0.91 specifically indicates that newer versions may already contain the necessary protections, though organizations must verify their software versions and ensure complete patch coverage across all network devices. Additionally, network administrators should implement intrusion detection systems that can identify suspicious EAP-TLS traffic patterns that might indicate exploitation attempts. The refusals of the `refuse-app` option mentioned in the vulnerability description provides a potential workaround for environments where patching cannot be immediately implemented, though this represents only a temporary solution rather than a permanent fix.
The broader implications of this vulnerability highlight the critical importance of input validation and memory safety in network protocol implementations. Security practitioners should recognize that vulnerabilities of this nature often stem from insufficient bounds checking and improper error handling in cryptographic protocol implementations. The fact that this issue affects EAP-TLS, a widely deployed authentication protocol, underscores the need for comprehensive security reviews of all network authentication mechanisms. Organizations must maintain continuous vigilance regarding software patches and updates, particularly for network infrastructure components that handle authentication and authorization processes. The vulnerability also demonstrates the importance of adhering to secure coding practices and conducting thorough security testing of protocol implementations before deployment in production environments.