CVE-2026-45905
Estado: En análisisMedia (4.7)—
In the Linux kernel, the following vulnerability has been resolved:
xfrm: fix ip_rt_bug race in icmp_route_lookup reverse path
icmp_route_lookup() performs multiple route lookups to find a suitable route for sending ICMP error messages, with special handling for XFRM (IPsec) policies.
The lookup sequence is: 1. First, lookup output route for ICMP reply (dst = original src) 2. Pass through xfrm_lookup() for policy check 3. If blocked (-EPERM) or dst is not local, enter "reverse path" 4.
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In reverse path, call xfrm_decode_session_reverse() to get fl4_dec which reverses the original packet's flow (saddr<->daddr swapped) 5. If fl4_dec.saddr is local (we are the original destination), use __ip_route_output_key() for output route lookup 6. If fl4_dec.saddr is NOT local (we are a forwarding node), use ip_route_input() to simulate the reverse packet's input path 7. Finally, pass rt2 through xfrm_lookup() with XFRM_LOOKUP_ICMP flag
The bug occurs in step 6: ip_route_input() is called with fl4_dec.daddr (original packet's source) as destination. If this address becomes local between the initial check and ip_route_input() call (e.g., due to concurrent "ip addr add"), ip_route_input() returns a LOCAL route with dst.output set to ip_rt_bug.
This route is then used for ICMP output, causing dst_output() to call ip_rt_bug(), triggering a WARN_ON:
Fix this by checking rt2->rt_type after ip_route_input(). If it's RTN_LOCAL, the route cannot be used for output, so treat it as an error.
The reproducer requires kernel modification to widen the race window, making it unsuitable as a selftest. It is available at:
Detalles técnicos trazas, registros y código del informe original
------------[ cut here ]------------ WARNING: net/ipv4/route.c:1275 at ip_rt_bug+0x21/0x30, CPU#1 Call Trace: <TASK> ip_push_pending_frames+0x202/0x240 icmp_push_reply+0x30d/0x430 __icmp_send+0x1149/0x24f0 ip_options_compile+0xa2/0xd0 ip_rcv_finish_core+0x829/0x1950 ip_rcv+0x2d7/0x420 __netif_receive_skb_one_core+0x185/0x1f0 netif_receive_skb+0x90/0x450 tun_get_user+0x3413/0x3fb0 tun_chr_write_iter+0xe4/0x220 ... https://gist.github.com/mrpre/eae853b72ac6a750f5d45d64ddac1e81
CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
- Puntuación base: 4.7
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.11%
- Percentil entre todas las CVEs puntuadas: 1
- Fecha de la puntuación: 6/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
Tecnologías afectadas (1)
CWE
- CWE-362
Referencias
- https://git.kernel.org/stable/c/1c9ef28f643cce34a6a6c36c8f4d6d60a60db7e1
- https://git.kernel.org/stable/c/2c1f59005da9dd4b07b26984fd719e36557dc57c
- https://git.kernel.org/stable/c/423ce12d10b426709489d6b84fdaa6d2f31c5652
- https://git.kernel.org/stable/c/81b84de32bb27ae1ae2eb9acf0420e9d0d14bf00
- https://git.kernel.org/stable/c/9a95ec9144eeff1fc6fbcc21b677e322c6f1430b
- https://git.kernel.org/stable/c/b04061f89ffc6168e7ec3c71d0086ec3c3797228
JSON original (NVD)
Mostrar
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: fix ip_rt_bug race in icmp_route_lookup reverse path\n\nicmp_route_lookup() performs multiple route lookups to find a suitable\nroute for sending ICMP error messages, with special handling for XFRM\n(IPsec) policies.\n\nThe lookup sequence is:\n1. First, lookup output route for ICMP reply (dst = original src)\n2. Pass through xfrm_lookup() for policy check\n3. If blocked (-EPERM) or dst is not local, enter \"reverse path\"\n4. In reverse path, call xfrm_decode_session_reverse() to get fl4_dec\n which reverses the original packet's flow (saddr<->daddr swapped)\n5. If fl4_dec.saddr is local (we are the original destination), use\n __ip_route_output_key() for output route lookup\n6. If fl4_dec.saddr is NOT local (we are a forwarding node), use\n ip_route_input() to simulate the reverse packet's input path\n7. Finally, pass rt2 through xfrm_lookup() with XFRM_LOOKUP_ICMP flag\n\nThe bug occurs in step 6: ip_route_input() is called with fl4_dec.daddr\n(original packet's source) as destination. If this address becomes local\nbetween the initial check and ip_route_input() call (e.g., due to\nconcurrent \"ip addr add\"), ip_route_input() returns a LOCAL route with\ndst.output set to ip_rt_bug.\n\nThis route is then used for ICMP output, causing dst_output() to call\nip_rt_bug(), triggering a WARN_ON:\n\n ------------[ cut here ]------------\n WARNING: net/ipv4/route.c:1275 at ip_rt_bug+0x21/0x30, CPU#1\n Call Trace:\n <TASK>\n ip_push_pending_frames+0x202/0x240\n icmp_push_reply+0x30d/0x430\n __icmp_send+0x1149/0x24f0\n ip_options_compile+0xa2/0xd0\n ip_rcv_finish_core+0x829/0x1950\n ip_rcv+0x2d7/0x420\n __netif_receive_skb_one_core+0x185/0x1f0\n netif_receive_skb+0x90/0x450\n tun_get_user+0x3413/0x3fb0\n tun_chr_write_iter+0xe4/0x220\n ...\n\nFix this by checking rt2->rt_type after ip_route_input(). If it's\nRTN_LOCAL, the route cannot be used for output, so treat it as an error.\n\nThe reproducer requires kernel modification to widen the race window,\nmaking it unsuitable as a selftest. It is available at:\n\n https://gist.github.com/mrpre/eae853b72ac6a750f5d45d64ddac1e81"
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