netfilter: ctnetlink: fix use-after-free in ctnetlink_dump_exp_ct()

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Summary

CVECVE-2026-23458
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-03 16:16:32 UTC
Updated2026-04-18 09:16:28 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: netfilter: ctnetlink: fix use-after-free in ctnetlink_dump_exp_ct() ctnetlink_dump_exp_ct() stores a conntrack pointer in cb->data for the netlink dump callback ctnetlink_exp_ct_dump_table(), but drops the conntrack reference immediately after netlink_dump_start(). When the dump spans multiple rounds, the second recvmsg() triggers the dump callback which dereferences the now-freed conntrack via nfct_help(ct), leading to a use-after-free on ct->ext. The bug is that the netlink_dump_control has no .start or .done callbacks to manage the conntrack reference across dump rounds. Other dump functions in the same file (e.g. ctnetlink_get_conntrack) properly use .start/.done callbacks for this purpose. Fix this by adding .start and .done callbacks that hold and release the conntrack reference for the duration of the dump, and move the nfct_help() call after the cb->args[0] early-return check in the dump callback to avoid dereferencing ct->ext unnecessarily. BUG: KASAN: slab-use-after-free in ctnetlink_exp_ct_dump_table+0x4f/0x2e0 Read of size 8 at addr ffff88810597ebf0 by task ctnetlink_poc/133 CPU: 1 UID: 0 PID: 133 Comm: ctnetlink_poc Not tainted 7.0.0-rc2+ #3 PREEMPTLAZY Call Trace: <TASK> ctnetlink_exp_ct_dump_table+0x4f/0x2e0 netlink_dump+0x333/0x880 netlink_recvmsg+0x3e2/0x4b0 ? aa_sk_perm+0x184/0x450 sock_recvmsg+0xde/0xf0 Allocated by task 133: kmem_cache_alloc_noprof+0x134/0x440 __nf_conntrack_alloc+0xa8/0x2b0 ctnetlink_create_conntrack+0xa1/0x900 ctnetlink_new_conntrack+0x3cf/0x7d0 nfnetlink_rcv_msg+0x48e/0x510 netlink_rcv_skb+0xc9/0x1f0 nfnetlink_rcv+0xdb/0x220 netlink_unicast+0x3ec/0x590 netlink_sendmsg+0x397/0x690 __sys_sendmsg+0xf4/0x180 Freed by task 0: slab_free_after_rcu_debug+0xad/0x1e0 rcu_core+0x5c3/0x9c0

Risk And Classification

EPSS: 0.000320000 probability, percentile 0.090980000 (date 2026-04-18)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected e844a928431fa8f1359d1f4f2cef53d9b446bf52 d8cd0efbccc5cfb0a80da744a7da76e1333ab925 git Not specified
CNA Linux Linux affected e844a928431fa8f1359d1f4f2cef53d9b446bf52 9821b47f669eb82791fa0b1a6ebaf9aa219bea72 git Not specified
CNA Linux Linux affected e844a928431fa8f1359d1f4f2cef53d9b446bf52 bdf2724eefd4455a66863abb025bab8d3aa98c57 git Not specified
CNA Linux Linux affected e844a928431fa8f1359d1f4f2cef53d9b446bf52 f04cc86d59906513d2d62183b882966fc0ae0390 git Not specified
CNA Linux Linux affected e844a928431fa8f1359d1f4f2cef53d9b446bf52 f025171feef2ac65663d7986f1d5ff0c28d6b2a9 git Not specified
CNA Linux Linux affected e844a928431fa8f1359d1f4f2cef53d9b446bf52 04c8907ce4e3d3e26c5e1a3e47aa5d17082cbb56 git Not specified
CNA Linux Linux affected e844a928431fa8f1359d1f4f2cef53d9b446bf52 cd541f15b60e2257441398cf495d978f816d09f8 git Not specified
CNA Linux Linux affected e844a928431fa8f1359d1f4f2cef53d9b446bf52 5cb81eeda909dbb2def209dd10636b51549a3f8a git Not specified
CNA Linux Linux affected 3.10 Not specified
CNA Linux Linux unaffected 3.10 semver Not specified
CNA Linux Linux unaffected 5.10.253 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.203 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.167 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.130 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.78 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.20 6.18.* semver Not specified
CNA Linux Linux unaffected 6.19.10 6.19.* semver Not specified
CNA Linux Linux unaffected 7.0 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/9821b47f669eb82791fa0b1a6ebaf9aa219bea72 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/04c8907ce4e3d3e26c5e1a3e47aa5d17082cbb56 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/bdf2724eefd4455a66863abb025bab8d3aa98c57 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/5cb81eeda909dbb2def209dd10636b51549a3f8a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/f04cc86d59906513d2d62183b882966fc0ae0390 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/cd541f15b60e2257441398cf495d978f816d09f8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/d8cd0efbccc5cfb0a80da744a7da76e1333ab925 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/f025171feef2ac65663d7986f1d5ff0c28d6b2a9 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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