CVE-2016-9555 in Linux
Summary
by MITRE • 01/25/2023
The sctp_sf_ootb function in net/sctp/sm_statefuns.c in the Linux kernel before 4.8.8 lacks chunk-length checking for the first chunk, which allows remote attackers to cause a denial of service (out-of-bounds slab access) or possibly have unspecified other impact via crafted SCTP data.
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Analysis
by VulDB Data Team • 01/25/2023
The vulnerability identified as CVE-2016-9555 represents a critical flaw in the Linux kernel's Stream Control Transmission Protocol implementation that affects versions prior to 4.8.8. This issue resides within the sctp_sf_ootb function located in net/sctp/sm_statefuns.c, which handles out-of-band data processing for SCTP connections. The vulnerability stems from inadequate validation of chunk lengths in the initial SCTP chunk received during connection establishment, creating a potential pathway for malicious actors to exploit the system's memory management mechanisms.
The technical exploitation of this vulnerability occurs through the absence of proper chunk-length verification for the first SCTP chunk processed by the kernel's SCTP state machine. When a remote attacker sends crafted SCTP packets with malformed chunk length fields, the kernel's sctp_sf_ootb function fails to validate these lengths before proceeding with memory operations. This oversight allows for out-of-bounds slab access, where the kernel attempts to read or write beyond the allocated memory boundaries for SCTP data structures. The flaw manifests as a denial of service condition that can crash the system or cause unpredictable behavior in the kernel's memory management subsystem.
From an operational perspective, this vulnerability presents significant risks to systems running affected Linux kernel versions, particularly those handling network communications through SCTP protocol. The impact extends beyond simple denial of service to potentially enabling more sophisticated attacks that could leverage the out-of-bounds memory access for privilege escalation or information disclosure. The vulnerability affects systems where SCTP is actively used for network communication, including telecommunications infrastructure, network equipment, and applications that rely on SCTP for reliable data transmission. The attack vector requires only the ability to send SCTP packets to the target system, making it particularly dangerous in network environments where SCTP traffic is common.
The underlying cause of this vulnerability aligns with CWE-129, which addresses improper validation of length fields, and can be mapped to ATT&CK technique T1059.005 for the potential to execute arbitrary code through kernel memory corruption. The vulnerability demonstrates a classic case of insufficient input validation that allows attackers to manipulate kernel data structures, potentially leading to system instability or compromise. Organizations should prioritize patching their Linux systems to kernel version 4.8.8 or later, as this update includes the necessary validation checks for SCTP chunk lengths. Additionally, network administrators should consider implementing network segmentation and monitoring to detect unusual SCTP traffic patterns that might indicate exploitation attempts, while also ensuring that all systems handling SCTP communications are regularly updated to maintain security posture against similar vulnerabilities.