CVE-2025-71097
Full vulnerability record from the local CVENow database.
Description
In the Linux kernel, the following vulnerability has been resolved: ipv4: Fix reference count leak when using error routes with nexthop objects When a nexthop object is deleted, it is marked as dead and then fib_table_flush() is called to flush all the routes that are using the dead nexthop. The current logic in fib_table_flush() is to only flush error routes (e.g., blackhole) when it is called as part of network namespace dismantle (i.e., with flush_all=true). Therefore, error routes are not flushed when their nexthop object is deleted: # ip link add name dummy1 up type dummy # ip nexthop add id 1 dev dummy1 # ip route add 198.51.100.1/32 nhid 1 # ip route add blackhole 198.51.100.2/32 nhid 1 # ip nexthop del id 1 # ip route show blackhole 198.51.100.2 nhid 1 dev dummy1 As such, they keep holding a reference on the nexthop object which in turn holds a reference on the nexthop device, resulting in a reference count leak: # ip link del dev dummy1 [ 70.516258] unregister_netdevice: waiting for dummy1 to become free. Usage count = 2 Fix by flushing error routes when their nexthop is marked as dead. IPv6 does not suffer from this problem.
Severity
MEDIUM
CVSS score
5.5
(v3.1)
Vulnerability status
Modified
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2026-01-13 16:16:09.583000
Last modified
2026-10-19 19:17:11.570000
View original CVE JSON
{
"id": "CVE-2025-71097",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2026-01-13T16:16:09.583",
"lastModified": "2026-10-19T19:17:11.570",
"vulnStatus": "Modified",
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{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv4: Fix reference count leak when using error routes with nexthop objects\n\nWhen a nexthop object is deleted, it is marked as dead and then\nfib_table_flush() is called to flush all the routes that are using the\ndead nexthop.\n\nThe current logic in fib_table_flush() is to only flush error routes\n(e.g., blackhole) when it is called as part of network namespace\ndismantle (i.e., with flush_all=true). Therefore, error routes are not\nflushed when their nexthop object is deleted:\n\n # ip link add name dummy1 up type dummy\n # ip nexthop add id 1 dev dummy1\n # ip route add 198.51.100.1/32 nhid 1\n # ip route add blackhole 198.51.100.2/32 nhid 1\n # ip nexthop del id 1\n # ip route show\n blackhole 198.51.100.2 nhid 1 dev dummy1\n\nAs such, they keep holding a reference on the nexthop object which in\nturn holds a reference on the nexthop device, resulting in a reference\ncount leak:\n\n # ip link del dev dummy1\n [ 70.516258] unregister_netdevice: waiting for dummy1 to become free. Usage count = 2\n\nFix by flushing error routes when their nexthop is marked as dead.\n\nIPv6 does not suffer from this problem."
},
{
"lang": "es",
"value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nipv4: Corrección de fuga de contador de referencias al usar rutas de error con objetos nexthop\n\nCuando un objeto nexthop es eliminado, es marcado como muerto y luego se llama a fib_table_flush() para vaciar todas las rutas que están usando el nexthop muerto.\n\nLa lógica actual en fib_table_flush() es vaciar solo las rutas de error (p. ej., blackhole) cuando se llama como parte del desmantelamiento de un espacio de nombres de red (es decir, con flush_all=true). Por lo tanto, las rutas de error no se vacían cuando su objeto nexthop es eliminado:\n\n # ip link add name dummy1 up type dummy\n # ip nexthop add id 1 dev dummy1\n # ip route add 198.51.100.1/32 nhid 1\n # ip route add blackhole 198.51.100.2/32 nhid 1\n # ip nexthop del id 1\n # ip route show\n blackhole 198.51.100.2 nhid 1 dev dummy1\n\nComo tal, siguen manteniendo una referencia en el objeto nexthop que a su vez mantiene una referencia en el dispositivo nexthop, lo que resulta en una fuga de contador de referencias:\n\n # ip link del dev dummy1\n [ 70.516258] unregister_netdevice: waiting for dummy1 to become free. Usage count = 2\n\nCorrección vaciando las rutas de error cuando su nexthop es marcado como muerto.\n\nIPv6 no sufre de este problema."
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