High 7.8Published May 1, 2026

CVE-2026-43027netfilter: nf_conntrack_helper: pass helper to expect cleanup

Updated under an hour ago (Oct 27, 2026, 3:23 PM ET)

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It affects Linux and 4 other products. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conntrack_helper: pass helper to expect cleanup nf_conntrack_helper_unregister() calls nf_ct_expect_iterate_destroy() to remove expectations belonging to the helper being unregistered. However, it passes NULL instead of the helper pointer as the data argument, so expect_iter_me() never matches any expectation and all of them survive the cleanup. After unregister returns, nfnl_cthelper_del() frees the helper object immediately. Subsequent expectation dumps or packet-driven init_conntrack() calls then dereference the freed exp->helper, causing a use-after-free. Pass the actual helper pointer so expectations referencing it are properly destroyed before the helper object is freed. BUG: KASAN: slab-use-after-free in string+0x38f/0x430 Read of size 1 at addr ffff888003b14d20 by task poc/103 Call Trace: string+0x38f/0x430 vsnprintf+0x3cc/0x1170 seq_printf+0x17a/0x240 exp_seq_show+0x2e5/0x560 seq_read_iter+0x419/0x1280 proc_reg_read+0x1ac/0x270 vfs_read+0x179/0x930 ksys_read+0xef/0x1c0 Freed by task 103: The buggy address is located 32 bytes inside of freed 192-byte region [ffff888003b14d00, ffff888003b14dc0)

CVSS: 7.8 HIGH (v3.1, NVD)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness (CWE): Not given
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Linux
NVD analysis: Modified
Record last updated: Oct 14, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Linux Linux linux:linux (from the name)	from ac7b848390036dadd4351899d2a23748075916bd before 5cf28d5c8dcbbe8af6d3b145babe491906d7bad1; from ac7b848390036dadd4351899d2a23748075916bd before 504ba4168466c91210c45acdc332479cfd5f2da6; from ac7b848390036dadd4351899d2a23748075916bd before dc1739eff48e34cc71d4e2f03715493fbcebd8af; from ac7b848390036dadd4351899d2a23748075916bd before 2cf2737c85a2ba2b52024dafe68ffad2676f97be; from ac7b848390036dadd4351899d2a23748075916bd before 2c16e4d64dd91227742dfe196a3e7b0568bef65a; from ac7b848390036dadd4351899d2a23748075916bd before 620f3d14c1ef51d425060a3056ad8dbae8f998a3; from ac7b848390036dadd4351899d2a23748075916bd before 90bd7e8501349db3006d21fbc09df9ffcb172965; from ac7b848390036dadd4351899d2a23748075916bd before a242a9ae58aa46ff7dae51ce64150a93957abe65	CNA record
Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518_4_pn_dp_mfp (from the name)	from V3.1.6	CISA ADP
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518f_4_pn_dp_mfp (from the name)	from V3.1.6	CISA ADP
Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP siemens:siplus_s7_1500_cpu_1518_4_pn_dp_mfp (from the name)	from V3.1.6	CISA ADP
linux linux_kernel linux:linux_kernel	from 4.14 before 5.10.253; from 5.11 before 5.15.203; from 5.16 before 6.1.168; from 6.2 before 6.6.134; from 6.7 before 6.12.81; from 6.13 before 6.18.22; from 6.19 before 6.19.12; 7.0; and 5 more ranges	NVD

References

References

https://git.kernel.org/stable/c/5cf28d5c8dcbbe8af6d3b145babe491906d7bad1	patch
https://git.kernel.org/stable/c/504ba4168466c91210c45acdc332479cfd5f2da6	patch
https://git.kernel.org/stable/c/dc1739eff48e34cc71d4e2f03715493fbcebd8af	patch
https://git.kernel.org/stable/c/2cf2737c85a2ba2b52024dafe68ffad2676f97be	patch
https://git.kernel.org/stable/c/2c16e4d64dd91227742dfe196a3e7b0568bef65a	patch
https://git.kernel.org/stable/c/620f3d14c1ef51d425060a3056ad8dbae8f998a3	patch
https://git.kernel.org/stable/c/90bd7e8501349db3006d21fbc09df9ffcb172965	patch
https://git.kernel.org/stable/c/a242a9ae58aa46ff7dae51ce64150a93957abe65	patch
https://cert-portal.siemens.com/productcert/html/ssa-019113.html
https://cert-portal.siemens.com/productcert/html/ssa-082556.html
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The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.