CVE-2009-2698 in Linux
Summary
by MITRE
The udp_sendmsg function in the UDP implementation in (1) net/ipv4/udp.c and (2) net/ipv6/udp.c in the Linux kernel before 2.6.19 allows local users to gain privileges or cause a denial of service (NULL pointer dereference and system crash) via vectors involving the MSG_MORE flag and a UDP socket.
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Analysis
by VulDB Data Team • 02/03/2025
The vulnerability described in CVE-2009-2698 represents a critical flaw in the Linux kernel's UDP networking implementation that affects versions prior to 2.6.19. This issue resides within the udp_sendmsg function which handles UDP message sending operations in both IPv4 and IPv6 implementations. The vulnerability manifests when specific combinations of socket options and message flags are used, creating a dangerous condition that can be exploited by local attackers to either escalate privileges or cause system crashes. The flaw specifically involves improper handling of the MSG_MORE flag during UDP socket operations, which is a flag used to indicate that multiple messages will be sent to the same destination.
The technical exploitation of this vulnerability occurs through a NULL pointer dereference condition that arises when the UDP implementation processes UDP messages with the MSG_MORE flag set. When a local user crafts a specific sequence of socket operations involving UDP sockets and this particular flag, the kernel's udp_sendmsg function fails to properly validate or initialize certain pointers before dereferencing them. This leads to a kernel panic and system crash, effectively causing a denial of service condition that can bring the entire system to a halt. The vulnerability is particularly dangerous because it operates at the kernel level where privilege escalation is possible, meaning that an attacker with local access could potentially leverage this flaw to gain elevated system privileges.
The operational impact of CVE-2009-2698 extends beyond simple denial of service scenarios to include potential privilege escalation capabilities that could allow local attackers to execute arbitrary code with kernel-level privileges. This makes the vulnerability particularly severe in multi-user environments or systems where local access might be obtained through social engineering, compromised accounts, or other attack vectors. The vulnerability affects all Linux systems running kernel versions before 2.6.19, which includes many widely deployed server and desktop systems. The exploitation requires only local access to the system, making it relatively easy to target and potentially affecting a large number of installations that have not been properly updated.
Mitigation strategies for this vulnerability primarily focus on kernel updates and system maintenance practices. The most effective solution is to upgrade to Linux kernel version 2.6.19 or later where the vulnerability has been patched through proper pointer validation and initialization. System administrators should also implement proper monitoring and logging to detect potential exploitation attempts, as the system crash behavior can be used to identify when attacks are occurring. Additionally, organizations should consider implementing network segmentation and access controls to limit local user access where possible, though this does not address the core vulnerability. This vulnerability aligns with CWE-476 which describes NULL pointer dereference conditions, and represents a classic example of how improper input validation in kernel code can lead to severe security consequences. The ATT&CK framework would categorize this under privilege escalation techniques where local users can leverage kernel vulnerabilities to gain higher privileges, making it a significant concern for system security posture.