CVE-2026-53012

nexthop: fix IPv6 route referencing IPv4 nexthop

State: Published
Severity: Not scored
Published: Jun 24, 2026
Updated: Oct 15, 2026
Reserved: Jun 9, 2026

Description

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

nexthop: fix IPv6 route referencing IPv4 nexthop

syzbot reported a panic [1] [2].

When an IPv6 nexthop is replaced with an IPv4 nexthop, the has_v4 flag of all groups containing this nexthop is not updated. This is because nh_group_v4_update is only called when replacing AF_INET to AF_INET6, but the reverse direction (AF_INET6 to AF_INET) is missed.

This allows a stale has_v4=false to bypass fib6_check_nexthop, causing IPv6 routes to be attached to groups that effectively contain only AF_INET members. Subsequent route lookups then call nexthop_fib6_nh() which returns NULL for the AF_INET member, leading to a NULL pointer dereference.

Fix by calling nh_group_v4_update whenever the family changes, not just AF_INET to AF_INET6.

Reproducer: # AF_INET6 blackhole ip -6 nexthop add id 1 blackhole # group with has_v4=false ip nexthop add id 100 group 1 # replace with AF_INET (no -6), has_v4 stays false ip nexthop replace id 1 blackhole # pass stale has_v4 check ip -6 route add 2001:db8::/64 nhid 100 # panic ping -6 2001:db8::1

[1] https://syzkaller.appspot.com/bug?id=e17283eb2f8dcf3dd9b47fe6f67a95f71faadad0 [2] https://syzkaller.appspot.com/bug?id=8699b6ae54c9f35837d925686208402949e12ef3

Scores

The record has no CVSS score.

Weaknesses

The record names no weakness.

Affected Products

Product	Versions
LinuxLinux	7bf4796dd09984ad1612877a82d0d139c70ae27f to before ceffe81a0be92afc0cd1340bc8ca46559cce9bb4Affected 7bf4796dd09984ad1612877a82d0d139c70ae27f to before 9c2d6770a5f4545a307eb66979bef7656a34d621Affected 7bf4796dd09984ad1612877a82d0d139c70ae27f to before 6275796f22bb382f3e9aa58ed0b4ef7bdad78cb8Affected 7bf4796dd09984ad1612877a82d0d139c70ae27f to before aaac3bed034239e1d75732211d9b05f30b0b4f35Affected 7bf4796dd09984ad1612877a82d0d139c70ae27f to before ad85961004fd4bd2f31209ac4b07612c6cefb9e7Affected 7bf4796dd09984ad1612877a82d0d139c70ae27f to before 613c8f4a501421dd258b07ea614205d4e16ec845Affected 7bf4796dd09984ad1612877a82d0d139c70ae27f to before b3b7e850e1541f0520c4a12ec884255c30427ff6Affected 7bf4796dd09984ad1612877a82d0d139c70ae27f to before 29c95185ba32b621fbc3800fb86e7dc3edf5c2beAffected
LinuxLinux	5.3Affected before 5.3Not affected 5.10.258 through 5.10.Not affected 5.15.209 through 5.15.Not affected 6.1.175 through 6.1.Not affected 6.6.141 through 6.6.Not affected 6.12.91 through 6.12.Not affected 6.18.33 through 6.18.Not affected 7.0.10 through 7.0.*Not affected 7.1 and laterNot affected

Product

Versions

LinuxLinux

7bf4796dd09984ad1612877a82d0d139c70ae27f to before ceffe81a0be92afc0cd1340bc8ca46559cce9bb4Affected
7bf4796dd09984ad1612877a82d0d139c70ae27f to before 9c2d6770a5f4545a307eb66979bef7656a34d621Affected
7bf4796dd09984ad1612877a82d0d139c70ae27f to before 6275796f22bb382f3e9aa58ed0b4ef7bdad78cb8Affected
7bf4796dd09984ad1612877a82d0d139c70ae27f to before aaac3bed034239e1d75732211d9b05f30b0b4f35Affected
7bf4796dd09984ad1612877a82d0d139c70ae27f to before ad85961004fd4bd2f31209ac4b07612c6cefb9e7Affected
7bf4796dd09984ad1612877a82d0d139c70ae27f to before 613c8f4a501421dd258b07ea614205d4e16ec845Affected
7bf4796dd09984ad1612877a82d0d139c70ae27f to before b3b7e850e1541f0520c4a12ec884255c30427ff6Affected
7bf4796dd09984ad1612877a82d0d139c70ae27f to before 29c95185ba32b621fbc3800fb86e7dc3edf5c2beAffected

LinuxLinux

5.3Affected
before 5.3Not affected
5.10.258 through 5.10.*Not affected
5.15.209 through 5.15.*Not affected
6.1.175 through 6.1.*Not affected
6.6.141 through 6.6.*Not affected
6.12.91 through 6.12.*Not affected
6.18.33 through 6.18.*Not affected
7.0.10 through 7.0.*Not affected
7.1 and laterNot affected

References

Every record here comes from the CVE Program’s CVE List. © 1999–2026 The MITRE Corporation. CVE is a registered trademark of The MITRE Corporation. The records are reproduced under the CVE Program terms of use.