{"id":"CVE-2025-39980","title":"nexthop: Forbid FDB status change while nexthop is in a group","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nnexthop: Forbid FDB status change while nexthop is in a group\n\nThe kernel forbids the creation of non-FDB nexthop groups with FDB\nnexthops:\n\n # ip nexthop add id 1 via …","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 38428d68719c454d269cb03b776d8a4b0ad66111 < e1e87ac0daacd51f522ecd1645cd76b5809303ed","Linux >= 38428d68719c454d269cb03b776d8a4b0ad66111 < 0e7bfe7a268ccbd7859730c529161cafbf44637c","Linux >= 38428d68719c454d269cb03b776d8a4b0ad66111 < ec428fff792b7bd15b248dafca2e654b666b1304","Linux >= 38428d68719c454d269cb03b776d8a4b0ad66111 < 24046d31f6f92220852d393d510b6062843e3fbd","Linux >= 38428d68719c454d269cb03b776d8a4b0ad66111 < f0e49fd13afe9dea7a09a1c9537fd00cea22badb","Linux >= 38428d68719c454d269cb03b776d8a4b0ad66111 < 8dd4aa0122885f710930de135af2adc4ccc3238f","Linux >= 38428d68719c454d269cb03b776d8a4b0ad66111 < 390b3a300d7872cef9588f003b204398be69ce08","Linux 5.8"],"published":"2025-10-15","updated":"2026-09-08","sourceUpdated":"2026-09-08T08:42:41.996Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2025-39980","references":[{"url":"https://git.kernel.org/stable/c/e1e87ac0daacd51f522ecd1645cd76b5809303ed"},{"url":"https://git.kernel.org/stable/c/0e7bfe7a268ccbd7859730c529161cafbf44637c"},{"url":"https://git.kernel.org/stable/c/ec428fff792b7bd15b248dafca2e654b666b1304"},{"url":"https://git.kernel.org/stable/c/24046d31f6f92220852d393d510b6062843e3fbd"},{"url":"https://git.kernel.org/stable/c/f0e49fd13afe9dea7a09a1c9537fd00cea22badb"},{"url":"https://git.kernel.org/stable/c/8dd4aa0122885f710930de135af2adc4ccc3238f"},{"url":"https://git.kernel.org/stable/c/390b3a300d7872cef9588f003b204398be69ce08"}],"tags":["cve.org"],"epss":0.00211,"epssPercentile":0.10111,"ingestedAt":"2026-09-08T15:33:26.996Z","slug":"CVE-2025-39980","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nnexthop: Forbid FDB status change while nexthop is in a group\n\nThe kernel forbids the creation of non-FDB nexthop groups with FDB\nnexthops:\n\n # ip nexthop add id 1 via 192.0.2.1 fdb\n # ip nexthop add id 2 group 1\n Error: Non FDB nexthop group cannot have fdb nexthops.\n\nAnd vice versa:\n\n # ip nexthop add id 3 via 192.0.2.2 dev dummy1\n # ip nexthop add id 4 group 3 fdb\n Error: FDB nexthop group can only have fdb nexthops.\n\nHowever, as long as no routes are pointing to a non-FDB nexthop group,\nthe kernel allows changing the type of a nexthop from FDB to non-FDB and\nvice versa:\n\n # ip nexthop add id 5 via 192.0.2.2 dev dummy1\n # ip nexthop add id 6 group 5\n # ip nexthop replace id 5 via 192.0.2.2 fdb\n # echo $?\n 0\n\nThis configuration is invalid and can result in a NPD [1] since FDB\nnexthops are not associated with a nexthop device:\n\n # ip route add 198.51.100.1/32 nhid 6\n # ping 198.51.100.1\n\nFix by preventing nexthop FDB status change while the nexthop is in a\ngroup:\n\n # ip nexthop add id 7 via 192.0.2.2 dev dummy1\n # ip nexthop add id 8 group 7\n # ip nexthop replace id 7 via 192.0.2.2 fdb\n Error: Cannot change nexthop FDB status while in a group.\n\n[1]\nBUG: kernel NULL pointer dereference, address: 00000000000003c0\n[...]\nOops: Oops: 0000 [#1] SMP\nCPU: 6 UID: 0 PID: 367 Comm: ping Not tainted 6.17.0-rc6-virtme-gb65678cacc03 #1 PREEMPT(voluntary)\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-4.fc41 04/01/2014\nRIP: 0010:fib_lookup_good_nhc+0x1e/0x80\n[...]\nCall Trace:\n <TASK>\n fib_table_lookup+0x541/0x650\n ip_route_output_key_hash_rcu+0x2ea/0x970\n ip_route_output_key_hash+0x55/0x80\n __ip4_datagram_connect+0x250/0x330\n udp_connect+0x2b/0x60\n __sys_connect+0x9c/0xd0\n __x64_sys_connect+0x18/0x20\n do_syscall_64+0xa4/0x2a0\n entry_SYSCALL_64_after_hwframe+0x4b/0x53\n\n## Affected\n\n- `Linux >= 38428d68719c454d269cb03b776d8a4b0ad66111 < e1e87ac0daacd51f522ecd1645cd76b5809303ed`\n- `Linux >= 38428d68719c454d269cb03b776d8a4b0ad66111 < 0e7bfe7a268ccbd7859730c529161cafbf44637c`\n- `Linux >= 38428d68719c454d269cb03b776d8a4b0ad66111 < ec428fff792b7bd15b248dafca2e654b666b1304`\n- `Linux >= 38428d68719c454d269cb03b776d8a4b0ad66111 < 24046d31f6f92220852d393d510b6062843e3fbd`\n- `Linux >= 38428d68719c454d269cb03b776d8a4b0ad66111 < f0e49fd13afe9dea7a09a1c9537fd00cea22badb`\n- `Linux >= 38428d68719c454d269cb03b776d8a4b0ad66111 < 8dd4aa0122885f710930de135af2adc4ccc3238f`\n- `Linux >= 38428d68719c454d269cb03b776d8a4b0ad66111 < 390b3a300d7872cef9588f003b204398be69ce08`\n- `Linux 5.8`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}