CVE-2024-49949

Name of the Vulnerable Software and Affected Versions: Linux kernel versions prior to 6.6.58

Description: The issue is related to a potential underflow in the qdisc pkt len init() function when handling UFO (UDP Fragmentation Offload) packets. This occurs after specific commits that introduced sanity checks to detect malicious attempts from user space to create bad GSO (Generic Segmentation Offload) packets. However, these checks allowed user space to craft a GSO packet that could lead to a crash in fq codel. The crash happens because qdisc pkt len init() sets gso segs to 0 and later attempts to access a null pointer, resulting in a kernel NULL pointer dereference.

Recommendations: To resolve this issue, update the Linux kernel to version 6.6.58 or later. As a temporary workaround, consider disabling the fq codel queueing discipline until a patch is available. Restrict access to the vulnerable qdisc pkt len init() function to minimize the risk of exploitation. Avoid using the skb->len and hdr len variables in the affected API endpoints until the issue is resolved.