{"cve":"CVE-2026-45905","nvd":{"published":"2026-05-27T14:17:04.993","modified":"2026-06-24T16:28:18.513","status":"Undergoing Analysis","description":"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","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H","score":4.7},"cwes":["CWE-362"],"references":["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"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:36:28.938604137+00:00"},"epss":{"cve":"CVE-2026-45905","score":0.00111,"percentile":0.01334,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}