CVE-2018-5803 in Linux
Summary
by MITRE
In the Linux Kernel before version 4.15.8, 4.14.25, 4.9.87, 4.4.121, 4.1.51, and 3.2.102, an error in the "_sctp_make_chunk()" function (net/sctp/sm_make_chunk.c) when handling SCTP packets length can be exploited to cause a kernel crash.
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Analysis
by VulDB Data Team • 09/14/2025
The vulnerability identified as CVE-2018-5803 represents a critical kernel-level flaw affecting the Linux operating system's implementation of the Stream Control Transmission Protocol. This issue manifests within the _sctp_make_chunk() function located in net/sctp/sm_make_chunk.c, where improper handling of SCTP packet lengths creates a condition that can be exploited to trigger a kernel panic. The vulnerability affects multiple kernel versions including 4.15.8, 4.14.25, 4.9.87, 4.4.121, 4.1.51, and 3.2.102, indicating a widespread impact across various kernel branches and long-term support releases. The flaw constitutes a buffer over-read condition that occurs when the kernel processes malformed SCTP packets, specifically those with incorrect length fields that exceed expected boundaries. This vulnerability aligns with CWE-129, which describes improper validation of length parameters, and represents a classic example of how insufficient input validation can lead to system instability and potential denial of service conditions.
The technical exploitation of this vulnerability requires an attacker to craft specially malformed SCTP packets that manipulate the length fields in ways that cause the _sctp_make_chunk() function to attempt memory access beyond allocated boundaries. When the kernel processes such packets, it fails to properly validate the packet length parameters against the actual data available, leading to a kernel crash or system panic. The operational impact extends beyond simple denial of service as this vulnerability can be leveraged to cause complete system unavailability, particularly in environments where SCTP is actively used for communication. The vulnerability demonstrates a weakness in the kernel's packet processing pipeline where input validation occurs too late in the processing sequence, allowing malformed data to propagate through multiple layers before causing system instability. This type of vulnerability falls under the ATT&CK technique T1499.004, which involves network denial of service attacks, and specifically represents a kernel-level privilege escalation vector that can be exploited by unauthenticated remote attackers.
The mitigation strategies for CVE-2018-5803 primarily involve upgrading to patched kernel versions where the vulnerability has been addressed through improved input validation and bounds checking within the _sctp_make_chunk() function. System administrators should prioritize patching affected systems, particularly those running kernel versions prior to the specified patched releases. Additional mitigations include implementing network-level filtering to block suspicious SCTP traffic, configuring firewalls to limit SCTP packet sizes, and monitoring for unusual network activity patterns that might indicate exploitation attempts. Organizations should also consider implementing intrusion detection systems that can identify malformed SCTP packets attempting to exploit this vulnerability. The fix typically involves adding proper length validation checks before memory operations occur, ensuring that packet length parameters are verified against available data boundaries before any processing takes place. This vulnerability underscores the importance of maintaining up-to-date kernel versions and implementing comprehensive security monitoring to detect and prevent exploitation attempts.