CVE-2026-43025 (GCVE-0-2026-43025)
Vulnerability from cvelistv5
Published
2026-05-01 14:15
Modified
2026-08-05 12:25
Severity ?
7.3 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: netfilter: ctnetlink: ignore explicit helper on new expectations Use the existing master conntrack helper, anything else is not really supported and it just makes validation more complicated, so just ignore what helper userspace suggests for this expectation. This was uncovered when validating CTA_EXPECT_CLASS via different helper provided by userspace than the existing master conntrack helper: BUG: KASAN: slab-out-of-bounds in nf_ct_expect_related_report+0x2479/0x27c0 Read of size 4 at addr ffff8880043fe408 by task poc/102 Call Trace: nf_ct_expect_related_report+0x2479/0x27c0 ctnetlink_create_expect+0x22b/0x3b0 ctnetlink_new_expect+0x4bd/0x5c0 nfnetlink_rcv_msg+0x67a/0x950 netlink_rcv_skb+0x120/0x350 Allowing to read kernel memory bytes off the expectation boundary. CTA_EXPECT_HELP_NAME is still used to offer the helper name to userspace via netlink dump.
References
Impacted products
Vendor Product Version
Linux Linux Version: bd0779370588386e4a67ba5d0b176cfded8e6a53
Version: bd0779370588386e4a67ba5d0b176cfded8e6a53
Version: bd0779370588386e4a67ba5d0b176cfded8e6a53
Version: bd0779370588386e4a67ba5d0b176cfded8e6a53
Version: bd0779370588386e4a67ba5d0b176cfded8e6a53
Version: bd0779370588386e4a67ba5d0b176cfded8e6a53
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: ctnetlink: ignore explicit helper on new expectations\n\nUse the existing master conntrack helper, anything else is not really\nsupported and it just makes validation more complicated, so just ignore\nwhat helper userspace suggests for this expectation.\n\nThis was uncovered when validating CTA_EXPECT_CLASS via different helper\nprovided by userspace than the existing master conntrack helper:\n\n  BUG: KASAN: slab-out-of-bounds in nf_ct_expect_related_report+0x2479/0x27c0\n  Read of size 4 at addr ffff8880043fe408 by task poc/102\n  Call Trace:\n   nf_ct_expect_related_report+0x2479/0x27c0\n   ctnetlink_create_expect+0x22b/0x3b0\n   ctnetlink_new_expect+0x4bd/0x5c0\n   nfnetlink_rcv_msg+0x67a/0x950\n   netlink_rcv_skb+0x120/0x350\n\nAllowing to read kernel memory bytes off the expectation boundary.\n\nCTA_EXPECT_HELP_NAME is still used to offer the helper name to userspace\nvia netlink dump."
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              "value": "AV:L - The vulnerable path is reached by a local userspace netlink request to NETLINK_NETFILTER, specifically CT expectation creation or NFQUEUE verdict attachment. It is not directly reachable from remote network packets without a local netlink actor.\nAC:L - There is no race or victim-dependent condition; the attacker controls the netlink attributes, master conntrack, helper selection, and expectation class. On an affected configuration with conntrack helpers available, triggering the out-of-bounds read is deterministic.\nPR:L - nfnetlink requires CAP_NET_ADMIN via netlink_net_capable(), but that capability is attainable by an unprivileged user in a new user/network namespace on systems that allow user namespaces. Therefore this is low privilege rather than real init-namespace administrator privilege.\nUI:N - No victim action is required after the attacker has local execution and can send the crafted netlink messages. The trigger is entirely attacker driven.\nS:U - The bug affects kernel netfilter/conntrack state within the same kernel security authority. It does not cross a VM, IOMMU, or other separate security scope boundary.\nC:H - The helper mismatch lets CTA_EXPECT_CLASS be validated against one helper while nf_ct_expect_related_report indexes the master helper\u0027s expect_policy with that class, causing slab out-of-bounds reads of kernel memory adjacent to the policy array. Following the higher-severity rule for out-of-bounds reads, this is treated as high confidentiality impact.\nI:L - No direct arbitrary write or control-flow hijack primitive was evident, but the invalid expectation class can still be inserted and affect conntrack expectation accounting and timer behavior outside the intended helper policy. This supports limited integrity impact.\nA:H - The reported failure is a KASAN slab-out-of-bounds BUG in nf_ct_expect_related_report, and the crafted request can be issued repeatedly. A kernel oops/panic or reliable local denial of service is therefore a high availability impact."
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    "cveId": "CVE-2026-43025",
    "datePublished": "2026-05-01T14:15:27.103Z",
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