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CVE-2025-39980

nexthop: Forbid FDB status change while nexthop is in a group

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.245, 5.15.194, 6.1.155, 6.6.109, 6.12.50, and 1 more
None on Exploit-DB, Metasploit or GitHub

Summary

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

Timeline

  1. CVE published
  2. Record last updated

Affected versions

  • Linux Linux

    From 38428d68719c454d269cb03b776d8a4b0ad66111 · fixed in e1e87ac0daacd51f522ecd1645cd76b5809303ed; From 38428d68719c454d269cb03b776d8a4b0ad66111 · fixed in 0e7bfe7a268ccbd7859730c529161cafbf44637c; From 38428d68719c454d269cb03b776d8a4b0ad66111 · fixed in ec428fff792b7bd15b248dafca2e654b666b1304; From 38428d68719c454d269cb03b776d8a4b0ad66111 · fixed in 24046d31f6f92220852d393d510b6062843e3fbd; From 38428d68719c454d269cb03b776d8a4b0ad66111 · fixed in f0e49fd13afe9dea7a09a1c9537fd00cea22badb; From 38428d68719c454d269cb03b776d8a4b0ad66111 · fixed in 8dd4aa0122885f710930de135af2adc4ccc3238f; From 38428d68719c454d269cb03b776d8a4b0ad66111 · fixed in 390b3a300d7872cef9588f003b204398be69ce08

  • Linux Linux

    5.8

  • KernelLinux

    From 5.8.0 · fixed in 5.10.245; From 5.11.0 · fixed in 5.15.194; From 5.16.0 · fixed in 6.1.155; From 6.2.0 · fixed in 6.6.109; From 6.7.0 · fixed in 6.12.50; From 6.13.0 · fixed in 6.16.10

References 7

git.kernel.org