CVE-2024-56751
Status: ModifiedMedium (5.5)—
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:
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().
Read full descriptionShow less
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.
Technical details traces, logs and code from the original report
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
CVSS
- Version: 3.1
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Base score: 5.5
Exploitation probability (EPSS)
- Probability of exploitation in the next 30 days: 0.22%
- Percentile among all scored CVEs: 11
- Score date: 10/5/2026
EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).
Affected technologies (1)
CWEs
- NVD-CWE-noinfo
References
- https://git.kernel.org/stable/c/0e4c6faaef8a24b762a24ffb767280e263ef8e10
- https://git.kernel.org/stable/c/43e25adc80269f917d2a195f0d59f74cdd182955
- https://git.kernel.org/stable/c/77aa9855a878fb43f547ddfbda3127a1e88ad31a
- https://git.kernel.org/stable/c/a3c3f8a4d025acc8c857246ec2b812c59102487a
- https://git.kernel.org/stable/c/b2f26a27ea3f72f75d18330f76f5d1007c791848
- https://git.kernel.org/stable/c/eb02688c5c45c3e7af7e71f036a7144f5639cbfe
- https://lists.debian.org/debian-lts-announce/2025/03/msg00001.html
Raw JSON (NVD)
Show
{
"id": "CVE-2024-56751",
"cveTags": [],
"metrics": {
"cvssMetricV31": [
{
"type": "Primary",
"source": "nvd@nist.gov",
"cvssData": {
"scope": "UNCHANGED",
"version": "3.1",
"baseScore": 5.5,
"attackVector": "LOCAL",
"baseSeverity": "MEDIUM",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"integrityImpact": "NONE",
"userInteraction": "NONE",
"attackComplexity": "LOW",
"availabilityImpact": "HIGH",
"privilegesRequired": "LOW",
"confidentialityImpact": "NONE"
},
"impactScore": 3.6,
"exploitabilityScore": 1.8
}
]
},
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74",
"lessThan": "77aa9855a878fb43f547ddfbda3127a1e88ad31a",
"versionType": "git"
},
{
"status": "affected",
"version": "f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74",
"lessThan": "b2f26a27ea3f72f75d18330f76f5d1007c791848",
"versionType": "git"
},
{
"status": "affected",
"version": "f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74",
"lessThan": "43e25adc80269f917d2a195f0d59f74cdd182955",
"versionType": "git"
},
{
"status": "affected",
"version": "f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74",
"lessThan": "a3c3f8a4d025acc8c857246ec2b812c59102487a",
"versionType": "git"
},
{
"status": "affected",
"version": "f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74",
"lessThan": "0e4c6faaef8a24b762a24ffb767280e263ef8e10",
"versionType": "git"
},
{
"status": "affected",
"version": "f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74",
"lessThan": "eb02688c5c45c3e7af7e71f036a7144f5639cbfe",
"versionType": "git"
}
],
"programFiles": [
"net/ipv6/route.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "5.3"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "5.3",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.15.181",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.120",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.64",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.11.11",
"versionType": "semver",
"lessThanOrEqual": "6.11.*"
},
{
"status": "unaffected",
"version": "6.12.2",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.13",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"net/ipv6/route.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2024-12-29T12:15:08.640",
"references": [
{
"url": "https://git.kernel.org/stable/c/0e4c6faaef8a24b762a24ffb767280e263ef8e10",
"tags": [
"Patch"
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/43e25adc80269f917d2a195f0d59f74cdd182955",
"tags": [
"Patch"
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/77aa9855a878fb43f547ddfbda3127a1e88ad31a",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/a3c3f8a4d025acc8c857246ec2b812c59102487a",
"tags": [
"Patch"
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/b2f26a27ea3f72f75d18330f76f5d1007c791848",
"tags": [
"Patch"
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/eb02688c5c45c3e7af7e71f036a7144f5639cbfe",
"tags": [
"Patch"
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://lists.debian.org/debian-lts-announce/2025/03/msg00001.html",
"source": "af854a3a-2127-422b-91ae-364da2661108"
}
],
"vulnStatus": "Modified",
"weaknesses": [
{
"type": "Primary",
"source": "nvd@nist.gov",
"description": [
{
"lang": "en",
"value": "NVD-CWE-noinfo"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: release nexthop on device removal\n\nThe CI is hitting some aperiodic hangup at device removal time in the\npmtu.sh self-test:\n\nunregister_netdevice: waiting for veth_A-R1 to become free. Usage count = 6\nref_tracker: veth_A-R1@ffff888013df15d8 has 1/5 users at\n\tdst_init+0x84/0x4a0\n\tdst_alloc+0x97/0x150\n\tip6_dst_alloc+0x23/0x90\n\tip6_rt_pcpu_alloc+0x1e6/0x520\n\tip6_pol_route+0x56f/0x840\n\tfib6_rule_lookup+0x334/0x630\n\tip6_route_output_flags+0x259/0x480\n\tip6_dst_lookup_tail.constprop.0+0x5c2/0x940\n\tip6_dst_lookup_flow+0x88/0x190\n\tudp_tunnel6_dst_lookup+0x2a7/0x4c0\n\tvxlan_xmit_one+0xbde/0x4a50 [vxlan]\n\tvxlan_xmit+0x9ad/0xf20 [vxlan]\n\tdev_hard_start_xmit+0x10e/0x360\n\t__dev_queue_xmit+0xf95/0x18c0\n\tarp_solicit+0x4a2/0xe00\n\tneigh_probe+0xaa/0xf0\n\nWhile the first suspect is the dst_cache, explicitly tracking the dst\nowing the last device reference via probes proved such dst is held by\nthe nexthop in the originating fib6_info.\n\nSimilar to commit f5b51fe804ec (\"ipv6: route: purge exception on\nremoval\"), we need to explicitly release the originating fib info when\ndisconnecting a to-be-removed device from a live ipv6 dst: move the\nfib6_info cleanup into ip6_dst_ifdown().\n\nTested running:\n\n./pmtu.sh cleanup_ipv6_exception\n\nin a tight loop for more than 400 iterations with no spat, running an\nunpatched kernel I observed a splat every ~10 iterations."
},
{
"lang": "es",
"value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: ipv6: liberar el siguiente salto al eliminar el dispositivo. La CI está experimentando un bloqueo aperiódico en el momento de eliminar el dispositivo en la prueba automática pmtu.sh: unregister_netdevice: esperando a que veth_A-R1 se libere. Recuento de uso = 6 ref_tracker: veth_A-R1@ffff888013df15d8 tiene 1/5 usuarios en 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 Si bien el primer sospechoso es dst_cache, el seguimiento explícito del dst que debe la última referencia del dispositivo a través de sondas demostró que dicho dst se mantiene en el siguiente salto en el fib6_info de origen. Similar a el commit f5b51fe804ec (\"ipv6: route: purge exception on removal\"), necesitamos liberar explícitamente la información fib original al desconectar un dispositivo que se va a eliminar de un dst ipv6 activo: mueva la desinfección fib6_info a ip6_dst_ifdown(). Probado ejecutando: ./pmtu.sh cleanup_ipv6_exception en un bucle cerrado durante más de 400 iteraciones sin splat, ejecutando un kernel sin parchear Observé un splat cada ~10 iteraciones."
}
],
"lastModified": "2026-06-17T08:12:54.333",
"configurations": [
{
"nodes": [
{
"negate": false,
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "00376139-25FC-484F-BF0B-09AA1783B306",
"versionEndExcluding": "6.1.120",
"versionStartIncluding": "5.3"
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "CA16DEE3-ABEC-4449-9F4A-7A3DC4FC36C7",
"versionEndExcluding": "6.6.64",
"versionStartIncluding": "6.2"
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "21434379-192D-472F-9B54-D45E3650E893",
"versionEndExcluding": "6.11.11",
"versionStartIncluding": "6.7"
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "D8882B1B-2ABC-4838-AC1D-DBDBB5764776",
"versionEndExcluding": "6.12.2",
"versionStartIncluding": "6.12"
}
],
"operator": "OR"
}
]
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}