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.
En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta: net: ipv6: corrige el pánico cuando una ruta IPv4 referencia un nexthop IPv6 de loopback Cuando se crea un objeto nexthop IPv6 independiente con un dispositivo de loopback (p. ej., 'ip -6 nexthop add id 100 dev lo'), fib6_nh_init() lo clasifica erróneamente como una ruta de rechazo. Esto se debe a que los objetos nexthop no tienen prefijo de destino (fc_dst=::), lo que hace que fib6_is_reject() coincida con cualquier nexthop de loopback. La ruta de rechazo omite fib_nh_common_init(), dejando nhc_pcpu_rth_output sin asignar. Si una ruta IPv4 referencia posteriormente este nexthop, __mkroute_output() desreferencia nhc_pcpu_rth_output NULL y entra en pánico. Simplificar la verificación en fib6_nh_init() para que solo coincida con rutas de rechazo explícitas (RTF_REJECT) en lugar de usar fib6_is_reject(). La heurística de promoción de loopback en fib6_is_reject() se maneja por separado por ip6_route_info_create_nh(). Después de este cambio, los tres casos se comportan de la siguiente manera: 1. Ruta de rechazo explícita ('ip -6 route add unreachable 2001:db8::/64'): RTF_REJECT está configurado, entra en la ruta de rechazo, omite fib_nh_common_init(). Sin cambio de comportamiento. 2. Ruta de rechazo de loopback implícita ('ip -6 route add 2001:db8::/32 dev lo'): RTF_REJECT no está configurado, toma la ruta normal, se llama a fib_nh_common_init(). ip6_route_info_create_nh() aún lo promueve a rechazo posteriormente. nhc_pcpu_rth_output se asigna pero no se usa, lo cual es inofensivo. 3. Objeto nexthop independiente ('ip -6 nexthop add id 100 dev lo'): RTF_REJECT no está configurado, toma la ruta normal, se llama a fib_nh_common_init(). nhc_pcpu_rth_output se asigna correctamente, corrigiendo el fallo cuando las rutas IPv4 referencian este nexthop.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
| Attack Vector | LOCAL |
|---|---|
| Attack Complexity | LOW |
| Privileges Required | LOW |
| User Interaction | NONE |
| Scope | UNCHANGED |
| Confidentiality Impact | NONE |
| Integrity Impact | NONE |
| Availability Impact | HIGH |
| Source | Type | Description |
|---|---|---|
| [email protected] | Primary |
en
CWE-476
|
| Vendor | Product | Version | Update | Type |
|---|---|---|---|---|
| linux | linux_kernel | * | <built-in method update of dict object at 0x702bde4f0e40> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x702bde4f3940> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x702bcbbf5000> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x702bcbbf4240> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x702bde4f3900> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x702bcbbf6680> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x702bde4f2400> | Operating System |
| linux | linux_kernel | 7.0 | <built-in method update of dict object at 0x702bde4f0400> | Operating System |
| linux | linux_kernel | 7.0 | <built-in method update of dict object at 0x702bcbbf5a40> | Operating System |
| Vulnerable | CPE |
|---|---|
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:* |