CVE-2024-56751: Linux kernel · ipv6: release nexthop on device removal
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 5.5 Medium · fixed in 5.15.0-1088.95~20.04.1 : update Linux kernel when convenient.
Data as of 28 Oct 2026, 11:14 UTC
- Patch
- Available – fixed in 5.15.0-1088.95~20.04.1, 5.15.0-1094.103~20.04.1, 5.15.0-1087.96~20.04.2 +60
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 29 Dec 2024
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Patches and advisories
- ubuntu.com/security/notices/USN-7276-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7277-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7310-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7449-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7450-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7451-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7452-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7453-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7449-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7468-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7523-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7524-1 (opens in a new tab)
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 24.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azure-6.11pkg:deb/ubuntu/linux-azure-6.11?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azure-nvidiapkg:deb/ubuntu/linux-azure-nvidia?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
Description
In the Linux kernel, the following vulnerability has been resolved: ipv6: release nexthop on device removal The CI is hitting some aperiodic hangup at device removal time in the pmtu.sh self-test: unregister_netdevice: waiting for veth_A-R1 to become free. Usage count = 6 ref_tracker: veth_A-R1@ffff888013df15d8 has 1/5 users at dst_init+0x84/0x4a0 dst_alloc+0x97/0x150 ip6_dst_alloc+0x23/0x90 ip6_rt_pcpu_alloc+0x1e6/0x520 ip6_pol_route+0x56f/0x840 fib6_rule_lookup+0x334/0x630 ip6_route_output_flags+0x259/0x480 ip6_dst_lookup_tail.constprop.0+0x5c2/0x940 ip6_dst_lookup_flow+0x88/0x190 udp_tunnel6_dst_lookup+0x2a7/0x4c0 vxlan_xmit_one+0xbde/0x4a50 [vxlan] vxlan_xmit+0x9ad/0xf20 [vxlan] dev_hard_start_xmit+0x10e/0x360 __dev_queue_xmit+0xf95/0x18c0 arp_solicit+0x4a2/0xe00 neigh_probe+0xaa/0xf0 While the first suspect is the dst_cache, explicitly tracking the dst owing the last device reference via probes proved such dst is held by the nexthop in the originating fib6_info. Similar to commit f5b51fe804ec ("ipv6: route: purge exception on removal"), we need to explicitly release the originating fib info when disconnecting a to-be-removed device from a live ipv6 dst: move the fib6_info cleanup into ip6_dst_ifdown(). Tested running: ./pmtu.sh cleanup_ipv6_exception in a tight loop for more than 400 iterations with no spat, running an unpatched kernel I observed a splat every ~10 iterations.
References
- ubuntu.com/security/CVE-2024-56751 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2024-56751 (opens in a new tab)
- git.kernel.org/linus/eb02688c5c45c3e7af7e71f036a7144f5639cbfe (opens in a new tab)
- git.kernel.org/stable/c/0e4c6faaef8a24b762a24ffb767280e263ef8e10 (opens in a new tab)
- git.kernel.org/stable/c/43e25adc80269f917d2a195f0d59f74cdd182955 (opens in a new tab)
- git.kernel.org/stable/c/a3c3f8a4d025acc8c857246ec2b812c59102487a (opens in a new tab)
- git.kernel.org/stable/c/b2f26a27ea3f72f75d18330f76f5d1007c791848 (opens in a new tab)
- git.kernel.org/stable/c/eb02688c5c45c3e7af7e71f036a7144f5639cbfe (opens in a new tab)
- ubuntu.com/security/notices/USN-7276-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7277-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7310-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7449-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7450-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7451-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7452-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7453-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7449-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7468-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7523-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7524-1 (opens in a new tab)