CVE-2025-39980nexthop: Forbid FDB status change while nexthop is in a group
Updated under an hour ago ()
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In the Linux kernel, the following vulnerability has been resolved: nexthop: Forbid FDB status change while nexthop is in a group The kernel forbids the creation of non-FDB nexthop groups with FDB nexthops: # ip nexthop add id 1 via 192.0.2.1 fdb # ip nexthop add id 2 group 1 Error: Non FDB nexthop group cannot have fdb nexthops. And vice versa: # ip nexthop add id 3 via 192.0.2.2 dev dummy1 # ip nexthop add id 4 group 3 fdb Error: FDB nexthop group can only have fdb nexthops. However, as long as no routes are pointing to a non-FDB nexthop group, the kernel allows changing the type of a nexthop from FDB to non-FDB and vice versa: # ip nexthop add id 5 via 192.0.2.2 dev dummy1 # ip nexthop add id 6 group 5 # ip nexthop replace id 5 via 192.0.2.2 fdb # echo $? 0 This configuration is invalid and can result in a NPD [1] since FDB nexthops are not associated with a nexthop device: # ip route add 198.51.100.1/32 nhid 6 # ping 198.51.100.1 Fix by preventing nexthop FDB status change while the nexthop is in a group: # ip nexthop add id 7 via 192.0.2.2 dev dummy1 # ip nexthop add id 8 group 7 # ip nexthop replace id 7 via 192.0.2.2 fdb Error: Cannot change nexthop FDB status while in a group. [1] BUG: kernel NULL pointer dereference, address: 00000000000003c0 [...] Oops: Oops: 0000 [#1] SMP CPU: 6 UID: 0 PID: 367 Comm: ping Not tainted 6.17.0-rc6-virtme-gb65678cacc03 #1 PREEMPT(voluntary) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-4.fc41 04/01/2014 RIP: 0010:fib_lookup_good_nhc+0x1e/0x80 [...] Call Trace: <TASK> fib_table_lookup+0x541/0x650 ip_route_output_key_hash_rcu+0x2ea/0x970 ip_route_output_key_hash+0x55/0x80 __ip4_datagram_connect+0x250/0x330 udp_connect+0x2b/0x60 __sys_connect+0x9c/0xd0 __x64_sys_connect+0x18/0x20 do_syscall_64+0xa4/0x2a0 entry_SYSCALL_64_after_hwframe+0x4b/0x53
- CVSS
- Not yet scored
- Weakness (CWE)
- Not given
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Linux
- NVD analysis
- Deferred
- Record last updated
- Oct 15, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Linux Linux linux:linux (from the name) | from 38428d68719c454d269cb03b776d8a4b0ad66111 before e1e87ac0daacd51f522ecd1645cd76b5809303ed; 38428d68719c454d269cb03b776d8a4b0ad66111 builds before 0e7bfe7a268ccbd7859730c529161cafbf44637c; from 38428d68719c454d269cb03b776d8a4b0ad66111 before ec428fff792b7bd15b248dafca2e654b666b1304; 38428d68719c454d269cb03b776d8a4b0ad66111 builds before 24046d31f6f92220852d393d510b6062843e3fbd; from 38428d68719c454d269cb03b776d8a4b0ad66111 before f0e49fd13afe9dea7a09a1c9537fd00cea22badb; 38428d68719c454d269cb03b776d8a4b0ad66111 builds before 8dd4aa0122885f710930de135af2adc4ccc3238f; 38428d68719c454d269cb03b776d8a4b0ad66111 builds before 390b3a300d7872cef9588f003b204398be69ce08 | CNA record |
Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518f_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP siemens:siplus_s7_1500_cpu_1518_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
References
- https://git.kernel.org/stable/c/e1e87ac0daacd51f522ecd1645cd76b5809303ed
- https://git.kernel.org/stable/c/0e7bfe7a268ccbd7859730c529161cafbf44637c
- https://git.kernel.org/stable/c/ec428fff792b7bd15b248dafca2e654b666b1304
- https://git.kernel.org/stable/c/24046d31f6f92220852d393d510b6062843e3fbd
- https://git.kernel.org/stable/c/f0e49fd13afe9dea7a09a1c9537fd00cea22badb
- https://git.kernel.org/stable/c/8dd4aa0122885f710930de135af2adc4ccc3238f
- https://git.kernel.org/stable/c/390b3a300d7872cef9588f003b204398be69ce08
- https://cert-portal.siemens.com/productcert/html/ssa-019113.html
- https://cert-portal.siemens.com/productcert/html/ssa-457936.html
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.