In the Linux kernel, the following vulnerability has been resolved:
net: ipv6: clear suppressed fib6 rule result
fib6_rule_suppress() drops a suppressed route with ip6_rt_put_flags(),
but leaves res->rt6 pointing at the released rt6_info.
If no later rule supplies a replacement, fib6_rule_lookup() still sees
res.rt6 and returns that stale dst to its caller. A suppressing rule can
therefore leak a released route back to rt6_lookup(), and the next put
hits rcuref_put_slowpath() from dst_release().
Clear res->rt6 when suppressing the route so suppressed lookups fall
through to the null dst instead of reusing the released one.
CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS Score: 9.8
AV:N - fib6_rule_suppress() runs on every IPv6 route lookup via fib6_rule_lookup(), including ip6_route_input() for received packets and icmp6/icmpv6 redirect handlers; WireGuard/VPN servers commonly deploy suppress_prefixlength rules (wg-quick), so remote IPv6 traffic to those hosts reaches the bug.
AC:L - Once suppress_prefixlength IPv6 policy routing rules exist, any matching packet deterministically triggers fib6_rule_suppress() to release the route while leaving a stale res->rt6 pointer; no race or uncontrollable memory layout is required.
PR:N - Remote exploitation needs only the ability to send IPv6 packets through a host whose operator already configured suppress rules (e.g., wg-quick); CAP_NET_ADMIN is an admin deployment prerequisite, not attacker privilege on the target.
UI:N - No victim action is required beyond normal delivery of attacker-generated IPv6 traffic (or ICMPv6 redirect) to a host performing policy-route lookup.
S:U - The stale rt6_info/dst_entry UAF corrupts kernel heap memory within the same host security boundary; it is not a VM escape or cross-authority sandbox break.
C:H - Returning a released rt6_info leaves a dangling dst_entry in ip6_dst_cache; subsequent reads through ip6_dst_idev(), dst metrics, or error paths are classic slab UAF with attacker-influencable heap reuse via sustained IPv6 traffic.
I:H - Double-free/imbalanced rcuref put and post-free use of rt6_info fields give heap corruption primitives; UAF on dst/route cache objects is routinely leveraged for kernel write and control-flow hijack.
A:H - Commit explicitly reports rcuref_put_slowpath() WARN from dst_release() on the freed route; UAF and refcount corruption can oops/panic the kernel, fully denying availability.
| Attack Vector |
Network |
Scope |
Unchanged |
| Attack Complexity |
Low |
Confidentiality Impact |
High |
| Privileges Required |
None |
Integrity Impact |
High |
| User Interaction |
None |
Availability Impact |
High |
AV:N - fib6_rule_suppress() runs on every IPv6 route lookup via fib6_rule_lookup(), including ip6_route_input() for received packets and icmp6/icmpv6 redirect handlers; WireGuard/VPN servers commonly deploy suppress_prefixlength rules (wg-quick), so remote IPv6 traffic to those hosts reaches the bug.
AC:L - Once suppress_prefixlength IPv6 policy routing rules exist, any matching packet deterministically triggers fib6_rule_suppress() to release the route while leaving a stale res->rt6 pointer; no race or uncontrollable memory layout is required.
PR:N - Remote exploitation needs only the ability to send IPv6 packets through a host whose operator already configured suppress rules (e.g., wg-quick); CAP_NET_ADMIN is an admin deployment prerequisite, not attacker privilege on the target.
UI:N - No victim action is required beyond normal delivery of attacker-generated IPv6 traffic (or ICMPv6 redirect) to a host performing policy-route lookup.
S:U - The stale rt6_info/dst_entry UAF corrupts kernel heap memory within the same host security boundary; it is not a VM escape or cross-authority sandbox break.
C:H - Returning a released rt6_info leaves a dangling dst_entry in ip6_dst_cache; subsequent reads through ip6_dst_idev(), dst metrics, or error paths are classic slab UAF with attacker-influencable heap reuse via sustained IPv6 traffic.
I:H - Double-free/imbalanced rcuref put and post-free use of rt6_info fields give heap corruption primitives; UAF on dst/route cache objects is routinely leveraged for kernel write and control-flow hijack.
A:H - Commit explicitly reports rcuref_put_slowpath() WARN from dst_release() on the freed route; UAF and refcount corruption can oops/panic the kernel, fully denying availability.
CVSS 3.1