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

netfilter: ip6t rt: fix zero-address non-strict match out-of-bounds read

rt mt6 check() permits rules to be configured with rtinfo->addrnr == 0 even when address matching (IP6T RT FST MASK) is requested.

In the IP6T RT FST NSTRICT path, rt mt6() evaluates packet routing addresses against rtinfo->addrs[i] and terminates backwards at the bottom of the loop:

if (ipv6 addr equal(ap, &rtinfo->addrs[i])) { i++; } if (i == rtinfo->addrnr) break;

When addrnr is 0, if the first packet address matches rtinfo->addrs[0], i is incremented to 1. Because i is now strictly greater than addrnr (0), the loop termination condition (i == rtinfo->addrnr) is bypassed and will never be satisfied.

If a crafted IPv6 packet contains matching routing addresses, i will advance past IP6T RT HOPS (16). The subsequent call to ipv6 addr equal() reads beyond struct ip6t rt, triggering UBSAN/KASAN out-of-bounds warnings or kernel panics.

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