cbcvebase.
CVE-2026-23300
published 2026-03-25

CVE-2026-23300: In the Linux kernel, the following vulnerability has been resolved: net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop When a standalone…

PriorityP420medium5.5CVSS 3.1
AVLACLPRLUINSUCNINAH
EPSS
0.13%
2.9th percentile
In the Linux kernel, the following vulnerability has been resolved: net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop When a standalone IPv6 nexthop object is created with a loopback device (e.g., "ip -6 nexthop add id 100 dev lo"), fib6_nh_init() misclassifies it as a reject route. This is because nexthop objects have no destination prefix (fc_dst=::), causing fib6_is_reject() to match any loopback nexthop. The reject path skips fib_nh_common_init(), leaving nhc_pcpu_rth_output unallocated. If an IPv4 route later references this nexthop, __mkroute_output() dereferences NULL nhc_pcpu_rth_output and panics. Simplify the check in fib6_nh_init() to only match explicit reject routes (RTF_REJECT) instead of using fib6_is_reject(). The loopback promotion heuristic in fib6_is_reject() is handled separately by ip6_route_info_create_nh(). After this change, the three cases behave as follows: 1. Explicit reject route ("ip -6 route add unreachable 2001:db8::/64"): RTF_REJECT is set, enters reject path, skips fib_nh_common_init(). No behavior change. 2. Implicit loopback reject route ("ip -6 route add 2001:db8::/32 dev lo"): RTF_REJECT is not set, takes normal path, fib_nh_common_init() is called. ip6_route_info_create_nh() still promotes it to reject afterward. nhc_pcpu_rth_output is allocated but unused, which is harmless. 3. Standalone nexthop object ("ip -6 nexthop add id 100 dev lo"): RTF_REJECT is not set, takes normal path, fib_nh_common_init() is called. nhc_pcpu_rth_output is properly allocated, fixing the crash when IPv4 routes reference this nexthop.

Affected

63 ranges· showing 25
VendorProductVersion rangeFixed in
debianlinux< linux 6.19.8-1 (forky)linux 6.19.8-1 (forky)
linuxlinux
linuxlinux>= 493ced1ac47c48bb86d9d4e8e87df8592be85a0e < 607e68c1b7c5a30c795571be1906d716e989a644607e68c1b7c5a30c795571be1906d716e989a644
linuxlinux>= 493ced1ac47c48bb86d9d4e8e87df8592be85a0e < c11d7c56c2076ee9cd72004f1976fe0734df2ae9c11d7c56c2076ee9cd72004f1976fe0734df2ae9
linuxlinux>= 493ced1ac47c48bb86d9d4e8e87df8592be85a0e < b5062fc2150614c9ea8a611c2e0cb6e047ebfa3ab5062fc2150614c9ea8a611c2e0cb6e047ebfa3a
linuxlinux>= 493ced1ac47c48bb86d9d4e8e87df8592be85a0e < b299121e7453d23faddf464087dff513a495b4fcb299121e7453d23faddf464087dff513a495b4fc
linuxlinux>= 493ced1ac47c48bb86d9d4e8e87df8592be85a0e < f7c9f8e3607440fe39300efbaf46cf7b5eecb23ff7c9f8e3607440fe39300efbaf46cf7b5eecb23f
linuxlinux>= 493ced1ac47c48bb86d9d4e8e87df8592be85a0e < b3b5a037d520afe3d5276e653bc0ff516bbda34cb3b5a037d520afe3d5276e653bc0ff516bbda34c
linuxlinux>= 493ced1ac47c48bb86d9d4e8e87df8592be85a0e < 8650db85b4259d2885d2a80fbc2317ce241941338650db85b4259d2885d2a80fbc2317ce24194133
linuxlinux>= 493ced1ac47c48bb86d9d4e8e87df8592be85a0e < 21ec92774d1536f71bdc90b0e3d052eff99cf09321ec92774d1536f71bdc90b0e3d052eff99cf093
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel>= 0 < 6.19.8-16.19.8-1
linuxlinux_kernel>= 5.11 < 5.15.2035.15.203
linuxlinux_kernel>= 5.16 < 6.1.1676.1.167
linuxlinux_kernel>= 5.3 < 5.10.2535.10.253
linuxlinux_kernel>= 5.3.0 < 6.1.1676.1.167
linuxlinux_kernel>= 6.13 < 6.18.176.18.17
linuxlinux_kernel>= 6.13.0 < 6.18.176.18.17
linuxlinux_kernel>= 6.19 < 6.19.76.19.7
linuxlinux_kernel>= 6.19.0 < 6.19.76.19.7
linuxlinux_kernel>= 6.2 < 6.6.1306.6.130
linuxlinux_kernel>= 6.2.0 < 6.6.1306.6.130
linuxlinux_kernel>= 6.7 < 6.12.776.12.77
linuxlinux_kernel>= 6.7.0 < 6.12.776.12.77

CVSS provenance

nvdv3.15.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
vendor_msrc7.5HIGH
vendor_ubuntu7.1HIGH
vendor_redhat5.5MEDIUM
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