In the Linux kernel, the following vulnerability has been resolved:

net: skbuff: fix pull-bound underflow in skb checksum setup ipv6()

skb maybe pull tail() subtracts skb headlen(skb) from the unsigned max argument and passes the result to pskb pull tail() as a signed int. The function does not ensure that max is at least skb headlen(skb).

This can happen while parsing IPv6 extension headers when an skb already has a linear area larger than MAX IPV6 HDR LEN. Once the parser needs data beyond the linear area, max - skb headlen(skb) wraps and is converted to a negative delta. pskb pull tail() then passes that negative length to skb copy bits(), where it can become a very large copy length.

Pass the requested length itself as the pull bound at the three extension-header call sites, so the delta can no longer go negative.