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National Vulnerability Database

National Vulnerability Database

NVD

National Vulnerability Database
  1. Vulnerabilities

CVE-2026-23300 Detail

Description

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.


Metrics

 
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CVSS 4.0 Severity and Vector Strings:

NIST CVSS score
NIST: NVD
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URL Source(s) Tag(s)
https://git.kernel.org/stable/c/21ec92774d1536f71bdc90b0e3d052eff99cf093 kernel.org
https://git.kernel.org/stable/c/607e68c1b7c5a30c795571be1906d716e989a644 kernel.org
https://git.kernel.org/stable/c/8650db85b4259d2885d2a80fbc2317ce24194133 kernel.org
https://git.kernel.org/stable/c/b299121e7453d23faddf464087dff513a495b4fc kernel.org
https://git.kernel.org/stable/c/b3b5a037d520afe3d5276e653bc0ff516bbda34c kernel.org
https://git.kernel.org/stable/c/b5062fc2150614c9ea8a611c2e0cb6e047ebfa3a kernel.org
https://git.kernel.org/stable/c/c11d7c56c2076ee9cd72004f1976fe0734df2ae9 kernel.org
https://git.kernel.org/stable/c/f7c9f8e3607440fe39300efbaf46cf7b5eecb23f kernel.org

Weakness Enumeration

CWE-ID CWE Name Source

Change History

2 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2026-23300
NVD Published Date:
03/25/2026
NVD Last Modified:
04/18/2026
Source:
kernel.org