netfilter: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent

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Summary

CVECVE-2026-43026
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-01 15:16:47 UTC
Updated2026-07-14 13:18:52 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: netfilter: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent ctnetlink_alloc_expect() allocates expectations from a non-zeroing slab cache via nf_ct_expect_alloc(). When CTA_EXPECT_NAT is not present in the netlink message, saved_addr and saved_proto are never initialized. Stale data from a previous slab occupant can then be dumped to userspace by ctnetlink_exp_dump_expect(), which checks these fields to decide whether to emit CTA_EXPECT_NAT. The safe sibling nf_ct_expect_init(), used by the packet path, explicitly zeroes these fields. Zero saved_addr, saved_proto and dir in the else branch, guarded by IS_ENABLED(CONFIG_NF_NAT) since these fields only exist when NAT is enabled. Confirmed by priming the expect slab with NAT-bearing expectations, freeing them, creating a new expectation without CTA_EXPECT_NAT, and observing that the ctnetlink dump emits a spurious CTA_EXPECT_NAT containing stale data from the prior allocation.

Risk And Classification

Primary CVSS: v3.1 5.5 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS: 0.000240000 probability, percentile 0.068060000 (date 2026-05-05)

Problem Types: NVD-CWE-noinfo

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 076a0ca02644657b13e4af363f487ced2942e9cb a5a89db6981a1ddf2314bf50cb49db5a3146185f git Not specified
CNA Linux Linux affected 076a0ca02644657b13e4af363f487ced2942e9cb 1c2ebdeff8d088a2e47ae25d7b38447249adace2 git Not specified
CNA Linux Linux affected 076a0ca02644657b13e4af363f487ced2942e9cb a64b7bf84b4d5ea54218c5d374ec87fff9000f43 git Not specified
CNA Linux Linux affected 076a0ca02644657b13e4af363f487ced2942e9cb 2898080c054ea4d6ddfaaf21bbedbc229a9a8376 git Not specified
CNA Linux Linux affected 076a0ca02644657b13e4af363f487ced2942e9cb fd002ff2ea030cbfb0188a11b3c60ce7f84485f4 git Not specified
CNA Linux Linux affected 076a0ca02644657b13e4af363f487ced2942e9cb 929f7a9a7aad9404a5867216c3f8738232355b38 git Not specified
CNA Linux Linux affected 076a0ca02644657b13e4af363f487ced2942e9cb bff0f4f06f12d6d9bc565a3e1378abd4f6f5ce36 git Not specified
CNA Linux Linux affected 076a0ca02644657b13e4af363f487ced2942e9cb 35177c6877134a21315f37d57a5577846225623e git Not specified
CNA Linux Linux affected 3.4 Not specified
CNA Linux Linux unaffected 3.4 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 6.1.168 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.134 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.81 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.22 6.18.* semver Not specified
CNA Linux Linux unaffected 6.19.12 6.19.* semver Not specified
CNA Linux Linux unaffected 7.0 * original_commit_for_fix Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.6 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.5 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.6 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.5 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP affected V3.1.6 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP affected V3.1.5 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP affected V3.1.6 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP affected V3.1.5 * custom Not specified
ADP Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.6 * custom Not specified
ADP Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.5 * custom Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/35177c6877134a21315f37d57a5577846225623e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/a5a89db6981a1ddf2314bf50cb49db5a3146185f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/fd002ff2ea030cbfb0188a11b3c60ce7f84485f4 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
cert-portal.siemens.com/productcert/html/ssa-082556.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e cert-portal.siemens.com
git.kernel.org/stable/c/bff0f4f06f12d6d9bc565a3e1378abd4f6f5ce36 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/929f7a9a7aad9404a5867216c3f8738232355b38 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/2898080c054ea4d6ddfaaf21bbedbc229a9a8376 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
cert-portal.siemens.com/productcert/html/ssa-019113.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e cert-portal.siemens.com
git.kernel.org/stable/c/1c2ebdeff8d088a2e47ae25d7b38447249adace2 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/a64b7bf84b4d5ea54218c5d374ec87fff9000f43 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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