CVE-2025-38463: 
Linux Kernel vulnerability analysis and mitigation

CVE-2025-38463 is a vulnerability in the Linux kernel related to TCP signedness issues in skb remaining space calculation. The vulnerability was discovered by Syzkaller and reported on July 25, 2025. It affects the TCP implementation in the Linux kernel, specifically involving the calculation of remaining space in socket buffers (NVD).

The vulnerability stems from a signedness issue in the TCP implementation where sk->skforwardalloc can overflow. The flaw occurs in the code that checks for available space in the skb using the calculation 'copy = sizegoal - skb->len'. Due to C's type promotion rules, the signed sizegoal is converted to an unsigned int before subtraction, resulting in potential integer overflow. The variables involved are: copy (ssizet/s64 on 64-bit systems), sizegoal (int), and skb->len (unsigned int). This conversion leads to copy always being non-negative, which can cause sk->skforwardalloc to overflow when handling large data transfers (NVD).

When exploited, this vulnerability can lead to memory allocation issues in the Linux kernel's TCP implementation. The overflow in sk->skforwardalloc can occur when sending large amounts of data (around 2GB) and sizegoal is adjusted to a value smaller than skb->len. This can result in sk->skforwardalloc being set to a value close to INTMAX, potentially causing it to wrap around and become negative during subsequent memory allocation requests (NVD).