Protocol checksum validation fails for IPv6 when an extension header precedes the protocol header. The checksum calculation incorrectly ignores the packet length offset (iph->len) that already includes the extension headers, allowing packets with such headers to be considered valid or to trigger errors. This flaw represents an incorrect handling of packet headers during checksum computation, which could be exploited to manipulate or disrupt network traffic.

The flaw exists in the Linux kernel across all distributions that use the open‑source Linux kernel until the patch committing 05cfe9863ef049d98141dc2969eefde72fb07625 or later is applied. No specific kernel versions are enumerated, so any version prior to receiving this commit is potentially affected.

The advisory provides no CVSS metric and the EPSS score is 0.00018, indicating a very low likelihood of exploitation. Because the vulnerability requires crafting IPv6 packets with extension headers, the attack vector is most likely remote network‑based. An attacker who succeeds could bypass checksum validation to transmit malformed packets, potentially leading to traffic manipulation or denial‑of‑service. Although no public exploit or KEV listing exists, the fact that the bug can affect global packet handling suggests a non‑negligible risk if the system remains unpatched.