CyberRota Analysis
AI-GeneratedThe vulnerability affects the Linux kernel's handling of TCP packets over IPv6, specifically related to the maximum segment size (MSS) when the maximum transmission unit (MTU) is large. This flaw can lead to a NULL pointer dereference when TCP packets are incorrectly interpreted due to the use of a magic value, potentially causing system crashes. Organizations using Linux-based systems, particularly those relying on IPv6 for networking, should prioritize applying the fix to mitigate the risk of service disruptions.
Original NVD Description
In the Linux kernel, the following vulnerability has been resolved: tcp: ipv6: clamp default adverting MSS to avoid GSO_BY_FRAGS (0xFFFF) When MTU is large, ip6_default_advmss() can return IPV6_MAXPLEN (65535). This is interpreted by TCP as mss_clamp, allowing the MSS to reach 65535. However, 0xFFFF is also used as a magic value GSO_BY_FRAGS in the kernel. If a TCP packet with gso_size=0xFFFF is passed to skb_segment(), it will be mistakenly treated as GSO_BY_FRAGS, leading to a NULL pointer dereference because local TCP packets do not use frag_list. Fix this by returning min(IPV6_MAXPLEN, GSO_BY_FRAGS - 1) (65534) from ip6_default_advmss() when MTU is large. Also update the stale comment in ip6_default_advmss() which suggested that IPV6_MAXPLEN is returned to mean "any MSS".