CVE-2024-41044 in Linux
Summary
by MITRE • 07/29/2024
In the Linux kernel, the following vulnerability has been resolved:
ppp: reject claimed-as-LCP but actually malformed packets
Since 'ppp_async_encode()' assumes valid LCP packets (with code from 1 to 7 inclusive), add 'ppp_check_packet()' to ensure that LCP packet has an actual body beyond PPP_LCP header bytes, and reject claimed-as-LCP but actually malformed data otherwise.
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Analysis
by VulDB Data Team • 10/09/2025
The vulnerability identified as CVE-2024-41044 resides within the Linux kernel's point-to-point protocol implementation, specifically affecting the ppp_async_encode function that handles asynchronous PPP packet encoding. This issue represents a critical flaw in packet validation mechanisms that could potentially allow malicious actors to exploit malformed network traffic. The vulnerability occurs when the system processes packets that are incorrectly identified as LCP (Link Control Protocol) frames but contain malformed data structures that do not conform to expected LCP packet specifications. The root cause stems from the assumption that all LCP packets processed by ppp_async_encode() contain valid code values ranging from 1 to 7 inclusive, without proper verification of the actual packet structure beyond the basic header.
The technical flaw manifests in the absence of comprehensive packet validation prior to processing LCP frames, creating a potential attack surface where malformed data can bypass initial checks. When the ppp_async_encode() function encounters packets that claim to be LCP but contain invalid or incomplete packet bodies, the system fails to properly validate the actual content structure. This oversight allows packets with valid LCP header codes but malformed payloads to proceed through the processing pipeline, potentially causing unexpected behavior or system instability. The vulnerability specifically affects the PPP (Point-to-Point Protocol) implementation in Linux kernels where the asynchronous encoding function makes assumptions about packet validity without sufficient verification mechanisms. This issue directly relates to CWE-129 Input Validation and CWE-20 Improper Input Validation, as the system fails to properly validate packet contents before processing them as legitimate LCP frames.
The operational impact of CVE-2024-41044 extends beyond simple packet processing errors, potentially enabling denial-of-service conditions or unauthorized access to network services that rely on PPP connections. Attackers could exploit this vulnerability by crafting specially formatted packets that appear to be valid LCP frames but contain malformed data structures designed to trigger system instability or bypass security controls. The vulnerability affects network infrastructure components that utilize PPP for authentication and connection management, including dial-up services, VPN connections, and network access control systems. When exploited, this flaw could allow adversaries to disrupt network services, cause system crashes, or potentially escalate privileges within systems that depend on proper PPP packet handling. The attack vector primarily involves network-based exploitation where malicious packets are transmitted through PPP connections, leveraging the insufficient validation to bypass normal security controls.
Mitigation strategies for CVE-2024-41044 focus on implementing proper packet validation mechanisms and ensuring that all LCP packets undergo comprehensive structure verification before processing. The recommended fix involves adding the ppp_check_packet() function to validate that LCP packets contain actual body content beyond the PPP_LCP header bytes, thereby preventing malformed packets from being processed as legitimate LCP frames. System administrators should prioritize updating affected Linux kernel versions to include the patched implementation that addresses this validation gap. Network security teams should implement monitoring solutions to detect unusual PPP packet patterns that might indicate exploitation attempts, while also ensuring proper network segmentation to limit potential attack impact. The fix aligns with ATT&CK technique T1071.004 Application Layer Protocol: DNS and T1210 Lateral Tool Transfer, as it addresses protocol-level vulnerabilities that could be exploited for network reconnaissance or lateral movement. Organizations should also consider implementing network access control lists to filter suspicious PPP traffic and maintain regular kernel updates to address similar vulnerabilities in the PPP implementation.