CVE-2011-1573 in Linux
Summary
by MITRE
net/sctp/sm_make_chunk.c in the Linux kernel before 2.6.34, when addip_enable and auth_enable are used, does not consider the amount of zero padding during calculation of chunk lengths for (1) INIT and (2) INIT ACK chunks, which allows remote attackers to cause a denial of service (OOPS) via crafted packet data.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 11/29/2021
The vulnerability described in CVE-2011-1573 represents a critical flaw in the Linux kernel's Stream Control Transmission Protocol implementation that affects versions prior to 2.6.34. This issue specifically targets the sctp subsystem within the kernel's networking stack, where the chunk length calculations for INIT and INIT ACK messages become corrupted due to improper handling of zero padding during packet processing. The vulnerability manifests when both addip_enable and auth_enable parameters are active, creating a scenario where the kernel fails to properly account for padding bytes when determining the actual length of SCTP chunks.
The technical root cause of this vulnerability lies in the net/sctp/sm_make_chunk.c file where the kernel's SCTP implementation incorrectly calculates chunk lengths by ignoring zero padding that may be present in the packet data. This miscalculation occurs during the processing of INIT and INIT ACK chunks, which are fundamental components of the SCTP handshake mechanism used to establish connections between endpoints. When attackers craft malicious packets containing specific padding patterns, the kernel's chunk length calculation routines produce incorrect values that can lead to memory corruption and system instability. The flaw operates at the protocol parsing layer where the kernel attempts to validate and process incoming SCTP packets, specifically failing to properly handle the padding that may be present in the chunk headers.
The operational impact of this vulnerability is severe as it enables remote attackers to trigger a kernel oops condition, which results in a system crash and denial of service. An attacker can exploit this vulnerability by sending carefully crafted SCTP packets that contain malformed padding in the INIT or INIT ACK chunks, causing the kernel to access invalid memory locations or attempt to process chunks with incorrect length parameters. This type of vulnerability is particularly dangerous in networked environments where SCTP is actively used, as it can be exploited by unauthorized users to disrupt services without requiring authentication or elevated privileges. The vulnerability affects systems running Linux kernel versions prior to 2.6.34, making it a widespread concern for organizations that have not yet updated their kernel versions.
This vulnerability aligns with CWE-129, which describes improper validation of length fields, and relates to the broader category of buffer overflows and memory corruption issues that can lead to denial of service conditions. From an ATT&CK perspective, this vulnerability maps to the T1499.004 technique for Network Denial of Service, specifically targeting the kernel's network stack implementation. The exploitability of this vulnerability is enhanced by the fact that it requires minimal privileges and can be triggered remotely, making it an attractive target for attackers seeking to disrupt network services. Organizations should prioritize updating to kernel versions 2.6.34 or later where this vulnerability has been addressed through proper padding calculation handling in the SCTP implementation.
The fix implemented in kernel version 2.6.34 involves correcting the chunk length calculation logic to properly account for zero padding in both INIT and INIT ACK chunks. This patch ensures that when the kernel processes these specific chunk types, it correctly calculates the total length including any padding bytes that may be present in the packet structure. The solution addresses the core issue by implementing proper length validation that considers the complete packet structure rather than assuming fixed or calculated lengths without accounting for padding variations that are legitimate within the SCTP protocol specification. This remediation aligns with best practices for protocol implementation and memory safety in kernel space code, ensuring that the SCTP subsystem properly validates and processes incoming packets according to the protocol's defined standards.