{"cve":"CVE-2026-23200","nvd":{"published":"2026-02-14T17:15:57.847","modified":"2026-06-17T10:21:05.217","status":"Analyzed","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: Fix ECMP sibling count mismatch when clearing RTF_ADDRCONF\n\nsyzbot reported a kernel BUG in fib6_add_rt2node() when adding an IPv6\nroute. [0]\n\nCommit f72514b3c569 (\"ipv6: clear RA flags when adding a static\nroute\") introduced logic to clear RTF_ADDRCONF from existing routes\nwhen a static route with the same nexthop is added. However, this\ncauses a problem when the existing route has a gateway.\n\nWhen RTF_ADDRCONF is cleared from a route that has a gateway, that\nroute becomes eligible for ECMP, i.e. rt6_qualify_for_ecmp() returns\ntrue. The issue is that this route was never added to the\nfib6_siblings list.\n\nThis leads to a mismatch between the following counts:\n\n- The sibling count computed by iterating fib6_next chain, which\n  includes the newly ECMP-eligible route\n\n- The actual siblings in fib6_siblings list, which does not include\n  that route\n\nWhen a subsequent ECMP route is added, fib6_add_rt2node() hits\nBUG_ON(sibling->fib6_nsiblings != rt->fib6_nsiblings) because the\ncounts don't match.\n\nFix this by only clearing RTF_ADDRCONF when the existing route does\nnot have a gateway. Routes without a gateway cannot qualify for ECMP\nanyway (rt6_qualify_for_ecmp() requires fib_nh_gw_family), so clearing\nRTF_ADDRCONF on them is safe and matches the original intent of the\ncommit.\n\n[0]:\nkernel BUG at net/ipv6/ip6_fib.c:1217!\nOops: invalid opcode: 0000 [#1] SMP KASAN PTI\nCPU: 0 UID: 0 PID: 6010 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025\nRIP: 0010:fib6_add_rt2node+0x3433/0x3470 net/ipv6/ip6_fib.c:1217\n[...]\nCall Trace:\n <TASK>\n fib6_add+0x8da/0x18a0 net/ipv6/ip6_fib.c:1532\n __ip6_ins_rt net/ipv6/route.c:1351 [inline]\n ip6_route_add+0xde/0x1b0 net/ipv6/route.c:3946\n ipv6_route_ioctl+0x35c/0x480 net/ipv6/route.c:4571\n inet6_ioctl+0x219/0x280 net/ipv6/af_inet6.c:577\n sock_do_ioctl+0xdc/0x300 net/socket.c:1245\n sock_ioctl+0x576/0x790 net/socket.c:1366\n vfs_ioctl fs/ioctl.c:51 [inline]\n __do_sys_ioctl fs/ioctl.c:597 [inline]\n __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583\n do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]\n do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94\n entry_SYSCALL_64_after_hwframe+0x77/0x7f","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":["CWE-476"],"references":["https://git.kernel.org/stable/c/50b7c7a255858a85c4636a1e990ca04591153dca","https://git.kernel.org/stable/c/b8ad2d53f706aeea833d23d45c0758398fede580","https://git.kernel.org/stable/c/bbf4a17ad9ffc4e3d7ec13d73ecd59dea149ed25","https://git.kernel.org/stable/c/d8143c54ceeba232dc8a13aa0afa14a44b371d93"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:23:35.260773158+00:00"},"epss":{"cve":"CVE-2026-23200","score":0.00133,"percentile":0.02819,"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."]}